bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional properties of monkey caudate neurons. I. Activities related to saccadic eye movements
Authors: Hikosaka O. , Sakamoto M. , Usui S.
Published: December 2017

1. We recorded single cell activities in the caudate nucleus of the monkeys trained to perform a series of visuomotor tasks. In the first part of this paper, we summarize the types and locations of neurons in the monkey caudate nucleus. In the second part, we report the characteristics of neurons related to saccadic eye movements. 2. Neurons were classified into two types in terms of spontaneous discharge pattern. A majority of the neurons (2,287/2,559, 89%) had very low-frequency discharges (mostly less than 1 Hz). The rest (n = 272) showed irregular-tonic discharges (3-8 Hz) with broad spikes. 3. Of 2,559 neurons tested, 867 showed spike activity related to some aspects of the tasks; 502 neurons showed discharges in response to environmental changes outside, not in relation to, the tasks. None of the neurons responsive in or outside the tasks belonged to the irregular-tonic type. 4. The task-related activities were classified as: Saccade-related, Visual, Auditory, Cognitive, Fixation-related, and Reward-related. The activities detected outside the tasks were classified into: Visual, Auditory, Movement-related, Reward-related, and Other. Few neurons had both task-related and task-unrelated activities. 5. The locations of recorded neurons were determined using a coordinate system based on the anterior and posterior commissures. Task-related neurons were clustered longitudinally in the central part of the caudate. Neurons responsive outside the tasks were more widely distributed; specifically, auditory neurons were in the medial part, whereas movement-related neurons were in the lateral part. The irregular-tonic neurons were dispersed all over the caudate. 6. The monkey was trained to fixate on a spot of light on the screen and, when the spot moved, to follow it by making a saccade. A visually guided saccade occurred when the spot moved to another location without a time gap (saccade task). A memory-guided saccade occurred when the spot first disappeared and after a time gap reappeared at a fixed location (saccade with gap task). By delivering a cue stimulus while the monkey was fixating, a memory-guided saccade was elicited to a randomly chosen location (delayed saccade task).(ABSTRACT TRUNCATED AT 400 WORDS)
Participation of prefrontal neurons in the preparation of visually guided eye movements in the rhesus monkey
Authors: Boch R. A. , Goldberg M. E.
Published: December 2017

1. We recorded from 257 neurons in the banks of the posterior third of the principal sulcus of two rhesus monkeys trained to look at a fixation point and make saccades to stimuli in the visual periphery. Sixty-six percent (220/257) discharged or were suppressed in association with one or more aspects of the tasks we used. 2. Fifty-eight percent (151/257) of the neurons responded to the appearance of a spot of light in some part of the contralateral visual field. Cells did not seem to have absolute requirements for stimulus shape, size, or direction of motion. 3. Thirty-six percent (29/79) of visually responsive neurons tested quantitatively gave an enhanced response to the stimulus in the receptive field when the monkey had to make a saccade to the stimulus when its appearance was synchronous with the disappearance of the fixation point (synchron task). Twenty-nine percent (19/57) of the neurons gave an enhanced response to the stimulus when the monkey had to make a saccade to the stimulus some time after it appeared (delayed-saccade task). In general, enhancement in the synchron task correlated well with enhancement in the delayed-saccade task. 4. Enhancement was spatially specific. It did not occur when the monkey made a saccade to a stimulus outside the receptive field even though there was a stimulus within the receptive field. 5. Twenty-three percent (27/117) of neurons studied in the delayed-saccade task gave two bursts, one at the appearance of the stimulus and a second one around the saccade. This second burst generally did not occur when the monkey made the same saccade to a remembered target, but instead required the presence of the visual stimulus, and so we describe it as a reactivation of the visual response. Reactivation was also spatially specific. 6. The latency from reactivation to the beginning of the saccade ranged from 160 ms before the saccade to the beginning of the saccade. Reactivation usually continued for several hundred milliseconds after the saccade, sometimes for the duration of the trial. 7. Reactivation and enhancement are not the same mechanism. Although some cells showed both phenomena there was no correlation between enhancement and reactivation. 8. Cells that showed reactivation in the saccade task also showed reactivation at a weaker level in a suppressed-saccade task. In this task the monkeys had to hold fixation despite the disappearance of the fixation point and the continued presence of the peripheral stimulus.(ABSTRACT TRUNCATED AT 400 WORDS)
Visually induced plasticity of postsaccadic ocular drift in normal humans
Authors: Kapoula Z. , Optican L. M. , Robinson D. A.
Published: December 2017

1. Five human subjects viewed binocularly the interior of a full-field hemisphere filled with a random-dot pattern. During training, eye movements were recorded by the electrooculogram. A computer detected the end of every saccade and immediately moved the pattern horizontally either in the same or, in different experiments, the opposite direction as the saccade. The motion was exponential, its amplitude was 25% of the horizontal component of the antecedent saccade, and its time constant was either 25, 50, or 100 ms in different experiments. Before and after 2-3 h of this experience, movements of both eyes were measured simultaneously by the eye-coil/magnetic-field method while subjects made saccades across the moveable pattern, looked between stationary targets, or made saccades in the dark, to see the effect of such adaptation on postsaccadic eye movements. 2. After 2-3 h (10,000-20,000 saccades) subjects developed a zero-latency, postsaccadic, ocular drift in the dark in the direction of the pattern motion. Three subjects were trained to backward drift, two to onward drift. Drift amplitude in the dark changed by 6% of the saccade size (range: 2-11%). The drift was exponential with an overall time constant of 108 ms. 3. After training, while viewing the adapting pattern motion, the change in the amplitude of the zero-latency drift was approximately 10% (range: 6.5-14%). 4. Increasing the time constant of the pattern motion produced significant increases in the time constant of the ocular drift. 5. The incidence of dynamic overshoot (a tiny, backward saccade immediately following a main saccade) was idiosyncratic and went up in some subjects and down in others with adaptation. These changes did not seem related to modifications of postsaccadic drift. 6. Normal human saccades are characterized by essentially no postsaccadic drift in the abducting eye and a pronounced onward drift (approximately 4%) in the adducting eye. This adduction-adduction asymmetry is largely preserved through adaptation. Thus the changes in drift were conjugate and conformed to Hering's law of equal (change of) innervation. 7. These results agree with those previously demonstrated in the monkey and can similarly be explained by parametric changes in the pulse, slide, and step of normal saccadic innervation.
Synaptic effects of intercostal tendon organs on membrane potentials of medullary respiratory neurons
Authors: Bolser D. C. , Remmers J. E.
Published: December 2017

1. Stimulation of intercostal muscle tendon organs or their afferent fibers reduces medullary inspiratory neuron activity, decreases motor output to inspiratory muscles, and increases the activity of expiratory laryngeal motoneurons. The present study examines the synaptic mechanisms underlying these changes to obtain information about medullary neurons that participate in the afferent limb of this reflex pathway. 2. Membrane potentials of medullary respiratory neurons were recorded in decerebrate paralyzed cats. Postsynaptic potentials (PSPs) elicited in these neurons by intercostal nerve stimulation (INS) were compared before and after intracellular iontophoresis of chloride ions. After chloride injection, the normal hyperpolarization caused by inhibitory (I) PSPs is "reversed" to depolarization. 3. In inspiratory neurons, reversal of IPSPs by chloride injection also reversed hyperpolarization produced by INS when applied during any portion of the respiratory cycle. This observation suggests that increased chloride conductance of the postsynaptic membrane mediated the inhibition. Further, it is very likely that the last-order interneuron in the afferent pathway must be excited by INS and alter inspiratory neuron activity via an inhibitory synapse. The linear relationship between the amplitude of the INS induced PSP and membrane potential of inspiratory neurons provided evidence that neurons in the afferent pathway are not respiratory modulated. 4. The membranes of expiratory vagal motoneurons and post-inspiratory neurons were depolarized by INS during all portions of the respiratory cycle before IPSP reversal. Reversal of IPSPs affected neither this depolarization of expiratory vagal motoneurons during stage I and II expiration nor that of post-inspiratory neurons during stage I expiration. Thus this depolarization probably resulted from synaptic excitation.(ABSTRACT TRUNCATED AT 250 WORDS)
Role of extracellular space in hyperosmotic suppression of potassium-induced electrographic seizures
Authors: Traynelis S. F. , Dingledine R.
Published: December 2017

1. Focal electrographic seizures arose in the CA1 region of rat hippocampal slices bathed in elevated (8.5 mM) external potassium [( K+]o). High [K+]o also induced spontaneous interictal bursts that originated in area CA3 and propagated to CA1. To examine the contribution to electrographic seizure initiation of excitatory mechanisms that are influenced by extracellular volume, we studied the effect of hyperosmotic expansion of interstitial volume on seizure occurrence, interictal bursts, and excitatory synaptic transmission. The tissue electrical resistance was also measured leading up to and during seizures. 2. Media made 5-30 mosmol/kg hyperosmotic by addition of agents restricted to the extracellular space (mannitol, sucrose, raffinose, L-glucose, dextran) rapidly and reversibly abolished [K+]o-induced spontaneous CA1 seizures in 86% of slices tested. However, similar increases in osmolality effected by agents that access the intracellular compartment (D-glucose, glycerol) did not influence electrographic seizure occurrence. Hyperosmotic changes with plasma membrane impermeable compounds, but not permeable compounds, produced significant concentration-dependent decreases (1-10%) in the electrical resistance of CA1 stratum pyramidale. Because tissue resistance is proportional to extracellular volume, these results suggest that hyperosmotic suppression of electrographic seizures is associated with expansion of the extracellular space in hippocampal slices. 3. Measurement of electrical resistance of the CA1 stratum pyramidale during spreading depression and electrographic seizure revealed an increase in tissue resistance to 122% and 108% of control, respectively. Furthermore, a slight (approximately 2%) but significant increase in electrical resistance gradually occurred over the 20 s immediately preceding seizure generation. The observed increase in tissue resistance suggests extracellular space is decreased during these events. 4. Hyperosmolality did not alter CA3 interictal burst frequency. However, burst intensity, estimated from the total length of the burst waveform, was significantly reduced in both the CA3 (83% control) and CA1 region (67% control) when osmotic changes were imposed by plasma membrane impermeant compounds. Additionally, media made hypoosmotic by removal of 7.5 mM NaCl reversibly increased burst intensity. 5. High [K+]o potentiated excitatory synaptic transmission and excitatory postsynaptic potential (EPSP) spike coupling.(ABSTRACT TRUNCATED AT 400 WORDS)
Electrophysiological characteristics of primate spinothalamic neurons with renal and somatic inputs
Authors: Ammons W. S.
Published: December 2017

1. Spinothalamic tract (STT) neurons in the T10-L3 segments were studied for responses to renal and somatic stimuli. A total of 90 neurons was studied in 25 alpha-chloralose anesthetized monkeys (Macaca fascicularis). All neurons were antidromically activated from the ventral posterior lateral nucleus of the thalamus. 2. Sixty-two cells were excited by renal nerve stimulation and six inhibited. Probability of locating cells with renal input was greatest in T11-L1. Cells were located in laminae I and IV-VII; however, most were located in laminae V-VII. Antidromic latencies averaged 4.61 +/- 0.32 (SE) ms, whereas antidromic conduction velocities averaged 43.23 +/- 9.03 m/s. 3. Cells with excitatory renal input received A delta input only (36 cells) or A delta- and C-fiber inputs (26 cells). Stimulation of A delta renal afferent fibers evoked bursts of 1-10 spikes/stimulus [mean 3.6 +/- 0.9 spikes/stimulus] with onset latencies of 10.7 +/- 0.5 ms. Stimulation of C-fibers evoked 1.3 +/- 0.5 spikes/stimulus with onset latencies of 61.7 +/- 11.1 ms. Magnitude of responses to A delta-fiber stimulation was greatest in T12 and decreased both rostrally and caudally. Inhibitory responses to renal nerve stimulation required activation of renal C-fibers. 4. All cells that responded to stimulation of renal afferent fibers received convergent inputs from somatic structures. Forty-four cells were classified as wide dynamic range, 10 were high threshold, 12 were high-threshold cells with inhibitory input from hair, 2 were deep, and 2 were low threshold. Somatic receptive fields were large and located on the flank and abdomen and/or the upper hindlimb. Fourteen cells had inhibitory receptive fields located on the contralateral hindlimb or one of the forearms. 5. It is concluded that T11-L1 STT cells in the monkey respond reliably to renal nerve stimulation. Thoracolumbar STT cells may thus play a role in pain that results from renal disease. The locations of the somatic receptive fields of the cells suggest that they are responsible for the referral of renal pain to the flank and abdomen.
Neuroendocrine bag cells of Aplysia are activated by bag cell peptide-containing neurons in the pleural ganglion
Authors: Brown R. O. , Pulst S. M. , Mayeri E.
Published: December 2017

1. The generation of egg-laying behavior in the marine mollusk Aplysia involves a prolonged burst discharge in the neuroendocrine bag cells, which secrete neuropeptides derived from the egg-laying hormone/bag cell peptide (ELH/BCP) precursor protein. 2. Besides the bag cells, which are located in the abdominal ganglion, small clusters of neurons in the cerebral and pleural ganglia also express the ELH/BCP neuropeptides. We made intracellular recordings from 32 of these ELH/BCP cells in right pleural ganglia, in 18 preparations, to characterize their physiological properties and their functional relationship to the bag cells. 3. The identification of these ELH/BCP cells was confirmed by pressure injection of Lucifer yellow and subsequent immunocytochemical processing for alpha-BCP immunoreactivity. 4. The basic electrophysiological properties of the pleural ELH/BCP cells were similar to those of the bag cells. These pleural cells were directly demonstrated to be electrically coupled, and direct intracellular stimulation of individual pleural ELH/BCP cells initiated prolonged, synchronous burst discharges in the entire cluster through a positive feedback mechanism. 5. Burst discharges elicited in the pleural ELH/BCP cells consistently initiated burst discharges in the bag cells. Bag cell burst discharges were less effective in initiating burst discharges in the pleural ELH/BCP cells, indicating that there were reciprocal but asymmetrical connections. 6. The results show that the pleural ELH/BCP cells are functionally coupled to the bag cells. They support the hypothesis that the pleural ELH/BCP cells are part of the descending pathway that initiates bag cell activity and egg-laying behavior, in vivo.
Physiological properties of sensory trigeminal neurons projecting to mesencephalic parabrachial area in the cat
Authors: Hayashi H. , Tabata T.
Published: December 2017

1. One hundred forty-one trigeminomesencephalic neurons in the sensory trigeminal nucleus of cats anesthetized with alpha-chloralose were identified by antidromic stimulation of the mesencephalic parabrachial area (PBA) which includes the nucleus cuneiformis, lateral periaqueductal gray matter, and the region between the inferior colliculus and brachium conjunctivum. 2. Neurons were categorized based on their responses to non-noxious and noxious mechanical and heat stimuli delivered to their peripheral receptive fields (RFs) including skin, mucosa, guard hairs, vibrissae, cornea, and tooth pulps. They were classified into three types: 48 nociceptive-specific (NS) neurons which responded to heavy pressure and/or noxious mechanical stimuli, and/or noxious radiant heat; 19 wide dynamic range (WDR) neurons which had a graded response to light tactile stimuli, noxious pinch, and/or noxious radiant heat; and 36 low-threshold mechanoreceptive (LTM) neurons which responded maximally to innocuous tactile stimuli. In subnucleus caudalis (Vc), NS and WDR neurons were the majority (75%) among the three types, while in the rostral subnuclei they were about one-half (54%) of the population. 3. The RFs were distributed over the orofacial and head region but mainly in the facial region. Twelve neurons (33% of the LTM neurons) responded to deflection of vibrissae and only 1 NS neuron out of 52 NS and WDR neurons tested responded to electrical stimulation of a tooth pulp. 4. A contralateral projection was dominant (57%), 30% projected ipsilaterally and 13% projected bilaterally.(ABSTRACT TRUNCATED AT 250 WORDS)
Responses of rat lateral hypothalamic neuronal activity to fastigial nucleus stimulation
Authors: Min B. I. , Oomura Y. , Katafuchi T.
Published: December 2017

1. The aim of this study was investigation of neuronal mechanisms underlying inputs from the fastigial nucleus (FN) to the lateral hypothalamic area (LHA). 2. In male anesthetized rats, 295 extracellular and 82 intracellular recordings of LHA responses to electrical stimulation of the FN, which elicited stimulus-locked pressor responses, were examined. 3. Contralateral FN stimulation evoked three types of responses in 48% of spontaneously firing LHA neurons: inhibition with 11 +/- 6 (SD) ms latency followed by excitation (30%), excitation with 15 +/- 12.5 ms latency (14%), and excitation followed by inhibition with 6 +/- 4 ms latency (4%). 4. Contralateral FN stimulation after transection of the inferior cerebellar peduncle (ICP), which resulted in a substantial fall of the fastigial pressor response, also evoked the three types of responses. These responses were unaffected by transection of the ICP. 5. Neuronal activity was recorded intracellularly from 82 LHA neurons, of which 36 (44%) responded to FN stimulation. Of the 36 neurons, 24 showed inhibitory postsynaptic potentials (IPSPs) with a mean latency of 7.5 +/- 2 ms. Of the 24 neurons, 16 were checked for change in IPSP latency with stimulus intensity, and 11 were considered to be monosynaptically connected since their latencies were constant when FN stimulation intensity was changed. The remaining 12 exhibited excitatory postsynaptic potentials (EPSPs) with a longer latency of 10.5 +/- 3 ms, which indicated polysynaptic conduction. The reversal potentials of the IPSP and EPSP were estimated to be about -77 mV and -13 mV, respectively. 6. Most glucose-sensitive neurons (78%), which were identified by their inhibition in response to electrophoretically applied glucose, were inhibited by FN stimulation, whereas only 7% of the glucose-insensitive neurons responded to such stimulation. 7. From the results, it was concluded that LHA neurons receive inhibitory monosynaptic and excitatory polysynaptic inputs from the FN via the superior cerebellar peduncle. These connections may contribute to hypothalamic modulation of feeding behavior.
Intraretinal analysis of the threshold dark-adapted ERG of cat retina
Authors: Frishman L. J. , Steinberg R. H.
Published: December 2017

1. The dark-adapted electroretinogram (ERG) obtained with 4-s flashes near threshold and at low intensities has three clear negative components: 1) a fast negative response at stimulus onset, 2) a slow negative response that increases in amplitude for about 2 s, and 3) a negative-going OFF response. The fast negative response was previously shown to originate from the scotopic threshold response (STR) arising in the proximal portion of neural retina. We investigated the intraretinal origins of the other two negative components and found that they also have origins in neural retina proximal to the photoreceptors. 2. In this study the ERG evoked in response to diffuse illumination of the dark-adapted cat retina was recorded between a chlorided silver wire in the vitreous and a plate behind the eye. Extracellular field potentials were recorded simultaneously with a microelectrode placed intraretinally at different retinal depths. In some cases light-dependent changes in extracellular K+ concentration ([K+]o) were recorded with the K+-selective barrel of a double-barreled microelectrode. 3. The three negative-going ERG potentials increased in amplitude from threshold up to approximately 6.0 log q.deg-2.s-1. The potential during illumination then became nearly flat, and the negative OFF response was exaggerated. At higher intensities, positive-going PII (DC-component and b-wave) and the c-wave emerged, whereas the a-wave (negative-going) was usually below threshold. 4. The slow negative ERG response was generated in neural retina, rather than by the retinal pigment epithelium. The response was positive-going in the transretinal recordings obtained in subretinal space. It was not, however, related to two positive-going responses from distal retina previously described as contributing negative components to the ERG: the neural retina component of the c-wave, termed slow PIII, and the rod-receptor potential. The slow negative response had a slower time course and lower threshold than slow PIII, and, more importantly, it was present in the absence of the [K+]o decrease in subretinal space that causes slow PIII. Furthermore, APB (1.2 mM vitreal concentration) blocked the entire negative-going ERG, whereas at higher intensities it blocked PII but not the c-wave in the ERG or slow PIII in transretinal recordings. These results indicate that the negative-going ERG components near threshold and at low intensities all originated proximal to the photoreceptors.(ABSTRACT TRUNCATED AT 400 WORDS)
Identification of two calcium currents in acutely dissociated neurons from the rat lateral geniculate nucleus
Authors: Hernandez-Cruz A. , Pape H. C.
Published: December 2017

1. Intracellular recording in the in vitro slice preparation and whole-cell, patch-clamp recording of acutely dissociated neurons from the rat lateral geniculate nucleus (LGN) were combined to study the Ca currents underlying their electrical responses. In slices from young animals (postnatal days 13-16), we found that dorsal LGN neurons have responses similar to those of adult preparations, including the presence of a low-threshold Ca spike (LTS). After enzymatic isolation of LGN neurons from the same animals, the firing properties appeared well preserved, as indicated by whole-cell, current-clamp recordings from dissociated multipolar cells (presumably geniculocortical relay neurons). 2. Two types of Ca currents were identified in voltage-clamped, isolated LGN neurons on the basis of their voltage dependency, pharmacology, and selectivity properties. These two currents resemble the low-voltage-activated (LVA) and high-voltage-activated (HVA) Ca channels found in rat sensory neurons (9). 3. The LVA current component required negative potentials (less than -80 mV) to deinactivate completely, started to activate around -60 mV and reached a plateau level around -25 mV. It peaked within 30-6 ms and decayed with a single time constant of approximately 24 ms at -20 mV. Its inactivation curve ranged from -100 to -40 mV, with a half-inactivation near -60 mV. The HVA current component could be isolated by holding the membrane potential positive to -60 mV, activated at potentials positive to -30 mV and peaked around +5 mV. The time-to-peak ranged from 30 to 6 ms in the voltage range from -30 to +35 mV and decayed very slowly with sustained depolarizing pulses (time constant ranged between 1,600 and 40 ms over the same voltage range). 4. The inactivation of LVA Ca current during depolarizing voltage steps was consistent with a voltage-dependent process. The recovery from inactivation after short (100 ms), inactivating prepulses displayed two exponential phases. The slower phase was predominant under conditions that induce large current flow through the membrane, suggesting a Ca-mediated mechanism. 5. The LVA current was preferentially blocked by 50 microM Ni2+, leaving the HVA currents almost unaltered. Fifty micromolars Cd2+, in contrast, seemed more effective in blocking the HVA component of the Ca current.(ABSTRACT TRUNCATED AT 400 WORDS)
Membrane properties of rat substantia gelatinosa neurons in vitro
Authors: Yoshimura M. , Jessell T. M.
Published: December 2017

1. The membrane properties of substantia gelatinosa (SG) neurons in an in vitro adult rat transverse spinal cord slice preparation with attached dorsal root have been examined. Intracellular recordings were obtained from identified SG neurons. 2. Seventy-six percent of SG neurons exhibited a time-dependent anomalous rectification (AR) when the membrane was hyperpolarized from the resting potential. The time-dependent AR was blocked by cesium (Cs+, 2 mM) but not by barium (Ba2+, 2 mM). Application of Cs+ itself caused membrane hyperpolarization in those SG neurons that expressed the time-dependent AR. The activation of the time-dependent AR was maximal at potentials 5-10 mV below the resting membrane potential. 3. In a few SG neurons, the current-voltage relationship revealed a marked inward rectification, even though there was no detectable time-dependent anomalous rectification during hyperpolarization. Analysis of the Ba2+- and Cs+-sensitivity of these neurons confirmed that SG neurons expressed two distinct ARs, one of which is fast and Ba2+-sensitive and the other of which is time-dependent and Ba2+-insensitive. 4. Fifty-one percent of SG neurons exhibited a transient outward rectification when hyperpolarizing current pulses were applied from potentials more positive than -60 mV or when depolarizing pulses were applied from potentials more negative than -65 mV. The transient outward rectification persisted for 0.3-2 s when hyperpolarizing pulses were applied at -55 mV. 5. The transient outward rectification was associated with a decrease in membrane resistance and was enhanced in low K+ solutions. 4-aminopyridine (4-AP, 2 mM) reversibly blocked the transient outward rectification. 6. The time-dependent anomalous and transient outward rectifying currents exerted opposite effects on the firing properties of SG neurons. Activation of the time-dependent AR increased neuronal excitability. In neurons that exhibited the time-dependent AR, membrane depolarization caused the appearance of a rebound depolarization that resulted in the generation of spikes with only a short delay after application of the depolarizing pulse. In contrast, the transient outward rectifying current markedly delayed spike firing in response to depolarizing pulses. This delay was blocked by application of 4-AP. 7. The diversity in response properties of subpopulations of SG neurons may result in part from this heterogeneity in membrane properties.
Maximal dentate gyrus activation: characteristics and alterations after repeated seizures
Authors: Stringer J. L. , Lothman E. W.
Published: December 2017

1. The dentate gyrus was activated by trains of stimulation to either the contralateral CA3 region or the ipsilateral angular bundle. Responses were monitored with recordings of extracellular field potentials and extracellular potassium ([K+]o. Maximal dentate activation was identified by the appearance of bursts of large-amplitude (20-40 mV) population spikes associated with a secondary rise in [K+]o and an abrupt negative shift of the DC potential. 2. Several parameters were defined to characterize features of maximal dentate activation. These included 1) time to onset of maximal dentate activation, 2) duration of maximal dentate activation, 3) stimulus threshold for maximal dentate activation, 4) threshold for afterdischarge production, and 5) afterdischarge durations. The time to onset of maximal dentate activation and the duration of maximal dentate activation depended on the stimulus intensity until, above a certain stimulus intensity, both parameters reached constant values. The total period of maximal dentate activation (during both stimulation and afterdischarge) was constant. 3. The characteristics of maximal dentate activation were then determined in kindled animals and compared with age-matched controls. Kindled animals had a significant increase in the total duration of maximal dentate activation and a decrease in the ratio of afterdischarge threshold to the threshold for maximal dentate activation to 1 from a ratio in control animals of 6. 4. In a set of urethan-anesthetized animals, the characteristics of maximal dentate activation before and after 36 stimuli were determined. One hour after the last of 36 stimulus-evoked seizures, there was a trend towards a decrease in the threshold for maximal dentate activation and in the time to its onset.(ABSTRACT TRUNCATED AT 250 WORDS)
Changes in membrane currents of hippocampal neurons evoked by brief anoxia
Authors: Krnjevic K. , Leblond J.
Published: December 2017

1. Effects of anoxia (2-4 min of 95% N2-5% CO2) on membrane currents of CA1 neurons were studied by single-electrode voltage clamp in hippocampal slices (from Sprague-Dawley rats) kept in an interface-type chamber at 33.5 degree. 2. When recording with KCl electrodes at a holding potential (VH) near-70 mV, anoxia evoked a slow outward current [0.18 +/- 0.06 (SE) nA], accompanied by a conductance increase ( + 46 +/- 20%, mean +/- SE). The difference current evoked by N2 had a reversal potential near-100 mV. It was much smaller in presence of 2-4 mM extracellular Cs, and any remaining outward current was abolished by 10 mM tetraethylammonium (TEA). Only inward currents were observed when recording with CsCl electrodes. 3. Inward relaxations evoked by large hyperpolarizing pulses from VH less than or equal to - 70 mV (Q-type) were not significantly depressed by anoxia (-1.5 +/- 6.0%). 4. Some voltage-dependent outward currents (evoked by 200-ms depolarizing pulses) were depressed during anoxia: 1) a fast-inactivating (A-like) current, obtained at VH less than or equal to -70 mV and suppressed by 200 microM 4-AP, was reduced by 25.6 +/- 7.3% (n = 5); 2) a slower, noninactivating (C-like) current, suppressed by TEA, was reduced by 52 +/- 7.2% (n = 16). Neither of these currents (1 or 2) was observed when recording with 2- to 3-M CsCl electrodes; and 3) small (M-like) inward relaxations, observed at VH approximately -40 mV 5. Net inward currents could be evoked after blockage of GK with 10 mM TEA when recording with KCl electrodes or by recording with CsCl electrodes. At VH less than or equal to -70 mV, large, transient, and incompletely controlled currents were evoked by depolarizing pulses; at VH less than or equal to -50 mV, smaller and more persistent currents were evoked by depolarizing pulses (L-like), and transient currents (T-like?) were seen immediately after hyperpolarizing pulses. 6.L-type currents (at VH less than or equal to -50 mV) were nearly abolished after 1-2 min anoxia (by approximately 90%). This was equally true of the currents evoked by constant pulses or peak currents in I-V plots. After reoxygenation, recovery was biphasic, with a quick early phase (to 50-80% in 2 min) and then a much slower one (to 60-90% by 10-15 min).(ABSTRACT TRUNCATED AT 400 WORDS)
Mutable and immutable features of paw-shake responses after hindlimb deafferentation in the cat
Authors: Koshland G. F. , Smith J. L.
Published: December 2017

1. Hindlimb paw-shake responses were assessed before and after unilateral deafferentation (L3-S1) in chronic-spinal cats (n = 5), spinalized at the T12 level 1 yr earlier. Selected ankle flexor [tibialis anterior (TA)] and extensor [lateral gastrocnemius (LG)] and knee extensor [vastus lateralis (VL)] muscles were surgically implanted with chronic electromyographic (EMG) electrodes to determine mutable features of cycle characteristics and muscle synergies that are modulated by motion-dependent feedback as opposed to immutable features that are centrally programmed and not modulated by limb afference. 2. Paw-shake responses were difficult to elicit in the extensively deafferented hindlimb; this was true particularly during the first recovery weeks after deafferentation. By the end of the first month, however, brief responses of 1 or 2 cycles were commonly elicited in four of five cats, and responses of 3-7 cycles were common by the end of the second month in three of five cats. Initially, responses in the deafferented limb were elicited by stimuli applied to the dorsolateral thigh, an oval patch of skin innervated by intact S2 afferents. Over the 4-mo recovery period, however, the receptive field of the largely denervated skin expanded, and responses were also elicited by stimuli applied to the lateral aspect of the knee and shank, but usually not the paw. 3. In addition to fewer average cycles per response (5 vs. 10 cycles), paw shaking evoked in the deafferented hindlimb was characterized by longer-than-average cycle periods (124 vs. 98 ms), but the average cycle period varied widely among responses, ranging from 99 to 239 ms. Before deafferentation, the temporal organization of consecutive cycles was stereotypic; cycle periods increased linearly throughout a response. After deafferentation, however, there was no systematic relationship between cycle period and cycle number, and approximately 14% of the records with greater than or equal to 3 cycles were characterized by arhythmical sequences of EMG bursts. 4. At the ankle, LG burst duration was not altered by deafferentation, but TA onset and burst duration were affected. Before deafferentation, TA onset was invariant with respect to the beginning of the cycle, and burst duration increased linearly with cycle period. After deafferentation, however, TA onset was delayed, and the delay increased linearly with cycle period. Consequently, the TA burst duration was brief and unrelated to cycle period.(ABSTRACT TRUNCATED AT 400 WORDS)
Chronic recordings from single sites of kitten striate cortex during experience-dependent modifications of receptive-field properties
Authors: Mioche L. , Singer W.
Published: December 2017

1. With the use of chronically implanted floating microelectrodes, we obtained simultaneous single-unit recordings from multiple sites in the kitten striate cortex and followed experience-dependent modifications of receptive-field properties. For induction of experimental modifications, we used the paradigm of monocular deprivation and reverse occlusion. Kittens were implanted when 4-5 wk old. During the following 2 days, receptive-field properties of the recorded units were determined once under light ketamine anesthesia and repeatedly while the kittens were awake and only lightly restrained. Subsequently, one eye was patched, and the resulting changes in neuronal eye preference were followed by repeated measurements of response properties. For investigation of the effects of reverse occlusion, the deprived eye was opened and the previously open eye closed when the neurons had become unresponsive to the initially deprived eye. Alternatively, kittens were monocularly deprived for 1 wk by lid suture before implantation. The closed eye was then opened, the other eye patched, and the effects of reverse occlusion were studied for up to 1 wk by repeated measurements of receptive-field properties. 2. The earliest effect of monocular deprivation was the disappearance of binocular summation, i.e., binocular responses ceased to be superior over monocular responses. Overt changes of ocular dominance were observed as early as 6 h after the beginning of monocular deprivation. These consisted of a gradual decrease of the excitatory response to deprived eye stimulation and, on occasions, of an additional moderate increase of responses to the normal eye. A complete loss of excitatory responses to deprived-eye stimulation was seen as early as 12 h after occlusion. In numerous cells, however, stimulation of the deprived eye continued to evoke inhibitory responses even after excitatory responses had vanished completely. During this shift in ocularity, neurons preserved their orientation and direction selectively. 3. The minimal time required for the manifestation of ocular dominance changes was similar regardless of whether the animals were stimulated continuously or were asleep part of the time, suggesting the existence of an experience-independent consolidation period for ocular dominance changes. 4. The first change after reverse occlusion was a reduction of the response to the newly deprived eye. The time course of this inactivation was similar to that observed after initial deprivation, whereas the recovery of responses to the previously deprived eye had a considerably slower time course.(ABSTRACT TRUNCATED AT 400 WORDS)
Cerebellar neuronal activity related to whole-arm reaching movements in the monkey
Authors: Fortier P. A. , Kalaska J. F. , Smith A. M.
Published: December 2017

1. Three monkeys were trained to make whole-arm reaching movements from a common central starting position toward eight radially arranged targets disposed at 45 degrees intervals. A sample of 312 cerebellar neurons with proximal-arm receptive fields or discharge related to shoulder or elbow movements was studied in the task. The sample included 69 Purkinje cells, 115 unidentified cortical cells, 65 interpositus neurons, and 63 dentate units. 2. The reaching task was divided into three movement-related epochs: a reaction time, a movement time, and holding over the target. All neurons demonstrated significant changes in discharge during one or more of these three epochs. Almost all of the cells (95%) showed a significant change in activity during the movement, whereas 68-69% of the cells showed significant changes from premovement activity during the reaction time and holding periods. 3. During the combined reaction time-movement period, 231/312 cells were strongly active in the task. Of these, 151 cells (65.4%) demonstrated unimodal directional responses. Sixty-three had a reciprocal relation to movement direction, whereas 88 showed only graded increases or decreases in activity. A further 37 cells (16.0%) were nondirectional, with statistically uniform changes in discharge in all eight directions. The remaining 43 cells (18.6%) showed significant differences in activity for different directions of movement, but their response patterns were not readily classifiable. 4. The proportion of directional versus nondirectional cells was consistent across the four cell populations. However, graded response patterns were more common and reciprocal responses less common among Purkinje and dentate neurons than among unidentified cortical cells and interpositus neurons. 5. The distribution of preferred directions of the population of cerebellar neurons covered all possible movement directions away from the common central starting position in the horizontal plane. When the preferred direction of each cell in the sample population was aligned, the mean direction-related activity of the cerebellar population formed a bell-shaped tuning curve for the activity recorded during both the reaction time and the movement, as well as during the time the arm maintained a fixed posture over the targets. A vector representation also showed that the overall activity of the cerebellar population during normal reaching arm movements generated a signal that varied with movement direction. 6. These results demonstrate that the cerebellum generates a signal that varies with the direction of movement of the proximal arm during normal aimed reaching movements and is consistent with a role in the control of the activity of muscles or muscle groups generating these movements.
Modulation of pursuit eye movements by stimulation of cortical areas MT and MST
Authors: Komatsu H. , Wurtz R. H.
Published: December 2017

1. Many cells in the superior temporal sulcus (STS) of the monkey that represent the foveal region of the visual field discharge during pursuit eye movements. Damage to these areas produces a deficit in the maintenance of pursuit eye movements when the target towards the side of the brain with the lesion. In the present experiments, we electrically stimulated these areas to better localize and understand the mechanisms underlying this directional pursuit deficit. 2. Monkeys were trained to pursue a moving target using a step-ramp task in which the target first stepped to an eccentric position and then moved smoothly across the screen. Trains of stimulation were applied after the monkey had begun to pursue the target to study stimulation effects of maintenance of pursuit. 3. Stimulation during pursuit frequently produced eye acceleration toward the side of the brain stimulated. Eye speed increased during pursuit toward the side stimulated and decreased during pursuit away from the side stimulated. This increase in velocity toward the side of the brain where stimulation presumably activated cells is consistent with the decrease in pursuit velocity toward the side of the brain after cells were removed by chemical lesions. 4. The increase or decrease in pursuit speed following stimulation produced a slip of the target on the retina. The pursuit system seemed to be insensitive to this slip during the period of stimulation, however, since the effect of stimulation during pursuit of a stabilized image (open-loop condition) was similar to that resulting from stimulation under normal pursuit conditions (closed-loop). This insensitivity to visual motion during stimulation suggests that the stimulation substitutes for that visual input. 5. The separation of eye and target position that resulted from stimulation did produce catch-up saccades. This provides added evidence that alteration of middle temporal area (MT) and medial superior temporal area (MST) modifies visual-motion but not visual-position information. 6. Stimulation that produced eye acceleration during pursuit produced only a slight effect during fixation of a stationary target. The effectiveness of the stimulation also increased as the speed of the pursuit increased between 5 and 25 degrees/s. These observations, which show that pursuit velocity altered the effect of stimulation, suggest that the stimulation acted on visual motion processing before information about the pursuit movement itself is incorporated. Since this stimulation produces directional pursuit effects, we hypothesize that the directional bias for pursuit originates in the visual signal conveyed to the pursuit system.(ABSTRACT TRUNCATED AT 400 WORDS)
Quantitative analysis of visual receptive fields of neurons in nucleus of the optic tract and dorsal terminal nucleus of the accessory optic tract in macaque monkey
Authors: Hoffmann K. P. , Distler C.
Published: December 2017

1. The visual receptive field properties of neurons in the nucleus of the optic tract (NOT) in the pretectum and the dorsal terminal nucleus (DTN) of the accessory optic tract were analyzed quantitatively in anesthetized, paralyzed macaque monkeys. 2. Visual latencies to reversals in direction of stimulus movement ranged from 40 to 80 ms [61 +/- 13.5 (SD) ms]. 3. All neurons increased their discharge rate during ipsiversive movement and decreased their ongoing activity during contraversive movement of single stimuli or whole-field random dot patterns. The population of neurons in the left NOT-DTN was excited most strongly by leftward movement pointing 4 degrees down; neurons in the right NOT-DTN were excited most strongly by rightward movement pointing 6 degrees down. The mean angle between the directions yielding the highest and the lowest discharge rate in the two populations of NOT-DTN neurons was 177 degrees. 4. The deviation of the preferred excitatory directions from the horizon in individual neurons varied with recording depth. Within the first 500 microns below the midbrain surface, neurons preferred near-horizontal directions, whereas neurons recorded more deeply preferred more oblique directions of stimulus movement. 5. The tuning widths of NOT-DTN neurons in the preferred excitatory direction were very broad. The mean halfwidth defined as the range of directions eliciting responses greater than 50% of the maximum was 127 +/- 25 degrees. 6. Moving a random dot pattern and a single bar of light simultaneously but in opposite directions caused NOT-DTN neurons to increase their discharge rate as soon as one of the two stimuli moved in the ipsiversive direction. The reduction in overall discharge rates when two stimuli moved in opposite directions indicates mainly inhibitory interactions. 7. All NOT-DTN neurons could be activated from both eyes. Interactions between the two eyes were modest and unspecific. Misalignment of the visual axes of the two eyes had no influence on response strength. 8. Optimal speeds of stimulus movement varied widely for different NOT-DTN neurons. The effective range of speeds to elicit direction-selective responses in the total population was very broad (0.1400 degrees/s. With oscillating horizontal stimulation, NOT-DTN neurons followed repetition rates up to 4 Hz at excursions of 40 degrees. Speeds greater than 500 degrees/s were either not effective or resulted in a suppression of ongoing activity in all directions of movement.(ABSTRACT TRUNCATED AT 400 WORDS)