bluuebunny/crossref_metadata_2025_split huggingface dataset:
Putting More Genetics into Genetic Algorithms
Authors: Burke Donald S. , De Jong Kenneth A. , Grefenstette John J. , Ramsey Connie Loggia , Wu Annie S. 
Published: February 2008

The majority of current genetic algorithms (GAs), while inspired by natural evolutionary systems, are seldom viewed as biologically plausible models. This is not a criticism of GAs, but rather a reflection of choices made regarding the level of abstraction at which biological mechanisms are modeled, and a reflection of the more engineering-oriented goals of the evolutionary computation community. Understanding better and reducing this gap between GAs and genetics has been a central issue in an interdisciplinary project whose goal is to build GA-based computational models of viral evolution. The result is a system called Virtual Virus (VIV). VIV incorporates a number of more biologically plausible mechanisms, including a more flexible genotype-to-phenotype mapping. In VIV the genes are independent of position, and genomes can vary in length and may contain noncoding regions, as well as duplicative or competing genes. Initial computational studies with VIV have already revealed several emergent phenomena of both biological and computational interest. In the absence of any penalty based on genome length, VIV develops individuals with long genomes and also performs more poorly (from a problem-solving viewpoint) than when a length penalty is used. With a fixed linear length penalty, genome length tends to increase dramatically in the early phases of evolution and then decrease to a level based on the mutation rate. The plateau genome length (i.e., the average length of individuals in the final population) generally increases in response to an increase in the base mutation rate. When VIV converges, there tend to be many copies of good alternative genes within the individuals. We observed many instances of switching between active and inactive genes during the entire evolutionary process. These observations support the conclusion that noncoding regions serve as scratch space in which VIV can explore alternative gene values. These results represent a positive step in understanding how GAs might exploit more of the power and flexibility of biological evolution while simultaneously providing better tools for understanding evolving biological systems.
The Recognition of Antonymy by a Language-Enriched Right Hemisphere
Authors: Gazzaniga Michael S. , Miller George A. 
Published: February 2008

Abstract
A commissurotomy patient with limited language in the right hemisphere was tested for ability to recognize direct and indirect antonyms. Normal subjects performing this task recognize direct antonyms faster than indirect. The patient's left hemisphere responded normally, but his right showed no difference in response to direct and indirect antonyms. It is concluded that the patient's right hemisphere had not learned that particular pairs of adjectives (the direct antonyms) can be used to represent the attribute whose contrasting values they express. Such learning normally occurs in the course of reasoning about attributes of things and events, but presumably failed to occur in this patient's right hemisphere because its powers of reasoning are severely limited.
Dream Bizarreness as the Cognitive Correlate of Altered Neuronal Behavior in REM Sleep
Authors: Mamelak Adam N. , Hobson J. Allan 
Published: February 2008

Abstract
Bizarreness is a cognitive feature common to REM sleep dreams, which can be easily measured. Because bizarreness is highly specific to dreaming, we propose that it is most likely brought about by changes in neuronal activity that are specific to REM sleep. At the level of the dream plot, bizarreness can be defined as either discontinuity or incongruity. In addition, the dreamer's thoughts about the plot may be logically deficient.
We propose that dream bizarreness is the cognitive concomitant of two kinds of changes in neuronal dynamics during REM sleep. One is the disinhibition of forebrain networks caused by the withdrawal of the modulatory influences of norepinephrine (NE) and serotonin (5HT) in REM sleep, secondary to cessation of firing of locus coeruleus and dorsal raphe neurons. This aminergic demodulation can be mathematically modeled as a shift toward increased error at the outputs from neural networks, and these errors might be represented cognitively as incongruities and/or discontinuities.
We also consider the possibility that discontinuities are the cognitive concomitant of sudden bifurcations or “jumps” in the responses of forebrain neuronal networks. These bifurcations are caused by phasic discharge of pontogeniculooccipital (PGO) neurons during REM sleep, providing a source of cholinergic modulation to the forebrain which could evoke unpredictable network responses. When phasic PGO activity stops, the resultant activity in the brain may be wholly unrelated to patterns of activity dominant before such phasic stimulation began. Mathematically such sudden shifts from one pattern of activity to a second, unrelated one is called a bifurcation. We propose that the neuronal bifurcations brought about by PGO activity might be represented cognitively as bizarre discontinuities of dream plot.
We regard these proposals as preliminary attempts to model the relationship between dream cognition and REM sleep neurophysiology. This neurophysiological model of dream bizarreness may also prove useful in understanding the contributions of REM sleep to the developmental and experiential plasticity of the cerebral cortex.
A Source Analysis of the Late Human Auditory Evoked Potentials
Authors: Scherg Michael , Vajsar Jiri , Picton Terence W. 
Published: February 2008

Abstract
The intracerebral generators of the human auditory evoked potentials were estimated using dipole source analysis of 14-channel scalp recordings. The response to a 400-msec toneburst presented every 0.9 sec could be explained by three major dipole sources in each temporal lobe. The first was a vertically oriented dipole located on the supratemporal plane in or near the auditory koniocortex. This contributed to the scalp-recorded N1 wave at 100 msec. The second was a vertically oriented dipole source located on the supratemporal plane somewhat anterior to the first. This contributed to both the Nl and the sustained potential (SP). The third was a laterally oriented dipole source that perhaps originated in the magnopyramidal temporal field. This contributed a negative wave to the lateral scalp recordings at the latency of 145 msec. A change in the frequency of the toneburst elicited an additional negativity in the scalp-recording —the mismatch negativity (MMN). When the frequency change was large, the mismatch negativity was composed of two distinct sources with sequential but partially overlapping activities. The earlier corresponded to the Nl dipole sources and the later to a more anteriorly located dipole with an orientation more lateral than Nl. Only the later source was active when the frequency change was small. MMN source activities peaked about 15 msec earlier in the contralateral hemisphere, while this difference was only 4 msec for the sources of the Nl.
Visual Search Performance in the Neglect Syndrome
Authors: Eglin Mirjam , Robertson Lynn C. , Knight Robert T. 
Published: February 2008

Abstract
Patients with hemispatial neglect fail to respond to stimuli on one side of space. We assessed to what extent the complexity and number of visual stimuli on both sides determine the severity of neglect. Patients with neglect were required to find specified targets in a cluttered visual field. Two sets of stimuli were used. One set produced effortless and parallel search performance in normal controls; the other set was more complex and produced serial search performance in normal controls. Both sets of stimuli resulted in a serial performance pattern in the patients. Their baseline search performance on both sides was similar when all stimulus items were restricted to one side. A pronounced difference between the two sides was evident when stimuli appeared on both sides. Search for targets on the intact side of space was unaffected by distractors on the neglected side, whereas search for targets on the neglected side was slowed disproportionately by distractors on the intact side. The slowing on the neglected side was more severe during the more demanding search task and when more items were present on the intact side. The results indicate that neglect is associated with an inability to move attention from objects on the intact side to items on the neglected side.
Neocortical Expansion: An Attempt toward Relating Phylogeny and Ontogeny
Authors: Killackey Herbert P. 
Published: February 2008

Abstract
The neocortex is the most characteristic feature of the human brain. On gross inspection, its convoluted surfaces can be seen to have overgrown and covered most other brain structures. In the functional sphere, it is to the neocortex that we attribute those behaviors assumed to be most uniquely human such as cognition and linguistic behavior. This essay is an attempt to understand how this structure expanded during the course of mammalian evolution. At present, any attempt must be more speculative than definitive, but it is offered in the hope that it will generate more discussion on a topic that is central to all neurobiology, as well as a number of allied disciplines. I will proceed by outlining current views on the evolution of the brain, briefly review the organization of the somatosensory cortex in several mammalian forms, and then discuss in some detail ontogenetic mechanisms that may have some bearing on neocortical phylogeny. The primary proposition put forth is that the mammalian neocortex is relatively unspecified by strict genetic means, and that this allowed the neocortex to expand and adapt to a variety of circumstances during the course of phylogeny.
Modulation of Spontaneous Brain Activity during Mental Imagery
Authors: Kaufman L. , Schwartz B. , Salustri C. , Williamson S. J. 
Published: February 2008

Abstract
Magnetic measurements of average power of human alpha and beta activity over the occipital and parietal areas of the scalp reveal spatially selective suppression of the activity of the occipital cortex when abstract figures are briefly presented visually and subjects simply indicate that they saw the figure. However, the duration of the suppression increases markedly when subjects must indicate whether or not they had previously seen the figure. The reaction time is similarly prolonged during the search of visual memory, and is commensurate with the duration of selective suppression of brain activity. It is also demonstrated that alpha activity is not replaced by beta activity during this suppression, but that power in the beta band is also diminished during memory search. Low correlations between the scalp distributions of power in the beta and alpha bands indicate that partly different neuronal populations give rise to activity of these different frequency bands. Since magnetic fields are negligibly affected by intervening bone tissues, dramatic asymmetries in the distribution of alpha activity across the scalps of individuals and the differences in distribution between individuals cannot be ascribed to differences in skull thickness but are due instead to differences in underlying brain anatomy or function. Nevertheless, a common pattern of suppression of alpha activity is observed across subjects during well-controlled cognitive tasks. This implies that the visual system is involved in mental imagery.
Receptive Field Characteristics That Allow Parietal Lobe Neurons to Encode Spatial Properties of Visual Input: A Computational Analysis
Authors: O'Reilly Randall C. , Kosslyn Stephen M. , Marsolek Chad J. , Chabris Christopher F. 
Published: February 2008

Abstract
A subset of visually sensitive neurons in the parietal lobe apparently can encode the locations of stimuli, whereas visually sensitive neurons in the inferotemporal cortex (area IT) cannot. This finding is puzzling because both sorts of neurons have large receptive fields, and yet location can be encoded in one case, but not in the other. The experiments reported here investigated the hypothesis that a crucial difference between the IT and parietal neurons is the spatial distribution of their response profiles. In particular, IT neurons typically respond maximally when stimuli are presented at the fovea, whereas parietal neurons do not. We found that a parallel-distributed-processing network could map a point in an array to a coordinate representation more easily when a greater proportion of its input units had response peaks off the center of the input array. Furthermore, this result did not depend on potentially implausible assumptions about the regularity of the overlap in receptive fields or the homogeneity of the response profiles of different units. Finally, the internal representations formed within the network had receptive fields resembling those found in area 7a of the parietal lobe.
The Cerebellum and Motor Learning
Authors: Glickstein Mitchell , Yeo Christopher 
Published: February 2008

Abstract
People with profound memory deficits can acquire new motor skills, even though on each day of training they may be unaware of having seen the training apparatus before. Similarly, rabbits can acquire or retain a conditioned nictitating membrane response despite massive lesions of the hippocampus or the cerebral cortex. Both lines of evidence suggest that sub-cortical structures may be sufficient for many forms of motor learning. One possible locus for motor learning is the cerebellum. This article traces the history of our knowledge of structure and function of the cerebellum. The anatomical and physiological evidence demonstrates that the cerebellum has the neural connections necessary to mediate simple forms of motor learning or reflex plasticity. Behavioral studies demonstrate that the cerebellum is involved in modification of the vestibuloocular reflex, recalibration of saccadic eye movements, and acquisition of the conditioned nictitating membrane response. Although the evidence in all three instances suggests that the cerebellum is important, there is no agreement as to whether the cerebellum is always necessary for motor learning or how it might participate. Two views are presented: one supporting the idea of the cerebellum as the locus for motor learning and the other opposing this idea. Some evidence that might resolve these disagreements is discussed.
Cortical Maturation and the Development of Visual Attention in Early Infancy
Authors: Johnson Mark H. 
Published: February 2008

AbstractBronson (1974) reviewed evidence in support of the claim that the development of visually guided behavior in the human infant over the first few months of life represents a shift from subcortical to cortical visual processing. Recently, this view has been brought into question for two reasons; first, evidence revealing apparently sophisticated perceptual abilities in the newborn, and second, increasing evidence for multiple cortica streams of visual processing. The present paper presents a reanalysis of the relation between the maturation of cortical pathways and the development of visually guided behavior, focusing in particular on how the maturational state of the primary visual cortex may constrain the functioning of neural pathways subserving oculomotor control.
The Pyramidal Cell and its Local-Circuit Interneurons: A Hypothetical Unit of the Mammalian Cerebral Cortex
Authors: Marín-Padilla Miguel 
Published: February 2008

Abstract
A pyramidal cell with five of its local-circuit interneurons (Cajal–Retzius, Martinotti, Cajal double-bouquet, basket, and chandelier cells), constitutes a distinct structural/functional assemblage of the mammalian neocortex. This pyramidal/local-circuit neuronal assemblage is proposed herein as a basic neocortical unit. This unit is shared by all mammals, embodies both specific structural as well as functional elements, and constitutes an essential developmental building block of the neocortex. In the model, the pyramidal cell represents a distinct, stable, projective, excitatory neuron that has remained essentially unchanged in the course of mammalian phylogeny. On the other hand, its local-circuit interneurons are more likely to be inhibitory and less stable, designed perhaps to adapt, and modify in response to environmental needs. The proposed model infers that the number of pyramidal cells contacted by each local-circuit interneuron as well as the number of synaptic contacts established with each one are elements acquired post-natally in response to individual needs. Thereby, the overall three-dimensional distribution and extent of these pyramidal/local-circuit neuronal assemblages should be species-specific, variable among individual of the same species, and able to adapt in response to environmental needs. The model introduces a different approach, perhaps a new vantage point, for the study of the basic structural organization of the mammalian cerebral cortex. Relationships of the proposed model to cortical function in general and to learning behavior in particular are discussed.
Hemispheric Mechanisms Controlling Voluntary and Spontaneous Facial Expressions
Authors: Gazzaniga Michael S. , Smylie Charlotte S. 
Published: February 2008

Abstract
The capacity of each disconnected cerebral hemisphere to control a variety of facial postures was examined in three split-brain patients. The dynamics of facial posturing were analyzed in 30-msec optical disc frames that were generated off videotape recordings of each patient's response to lateralized stimuli. The results revealed that commands presented to the left hemisphere effecting postures of the lower facial muscles showed a marked asymmetry, with the right side of the face sometimes responding up to 180 msec before the left side of the face. Commands presented to the right hemisphere elicited a response only if the posture involved moving the upper facial muscles. Spontaneous postures filmed during free conversation were symmetrical. The results suggest that while either hemisphere can generate spontaneous facial expressions only the left hemisphere is efficient at generating voluntaly expressions. This contrasts sharply with the fact that both hemispheres can carry out a wide variety of other voluntary movements with the hand and foot.
Amnesia due to Lesions Confined to the Hippocampus: A Clinical-Pathologic Study
Authors: Victor Maurice , Agamanolis Dimitri 
Published: February 2008

Abstract
Reported here is the case of a 65-year-old man who suffered a burst of severe, repetitive generalized seizures (status epilepticus). On recovery of consciousness he was left with a profound impairment of memory, which remained unchanged for the subsequent 30 months of his life. During this period the cognitive defect was fully documented. Careful neuropathologic examination disclosed the presence of remarkably discrete lesions, confined to the hippocampus on each side. Because of the rarity of well-documented instances of this type and their importance in the study of memory function, we are reporting our case in some detail.
Visual Object Representation: Interpreting Neurophysiological Data within a Computational Framework
Authors: Plaut David C. , Farah Martha J. 
Published: February 2008

Abstract
Significant progress has been made in understanding vision by combining computational and neuroscientific constraints. However, for the most part these integrative approaches have been limited to low-level visual processing. Recent advances in our understanding of high-level vision in the two separate disciplines warrant an attempt to relate and integrate these results to extend our understanding of vision through object representation and recognition. This paper is an attempt to contribute to this goal, by using a computational framework arising out of computer vision research to organize and interpret human and primate neurophysiology and neuropsychology.
Face-Selective Cells in the Temporal Cortex of Monkeys
Authors: Desimone Robert 
Published: February 2008

Abstract
The notion of a neuron that responds selectively to the image of a particular complex object has been controversial ever since Gross and his colleagues reported neurons in the temporal cortex of monkeys that were selective for the sight of a monkey's hand (Gross, Rocha-Miranda, & Bender, 1972). Since that time, evidence has mounted for neurons in the temporal lobe that respond selectively to faces. The present paper presents a critical analysis of the evidence for face neurons and discusses the implications of these neurons for models of object recognition. The paper also presents some possible reasons for the evolution of face neurons and suggests some analogies with the development of language in humans.
Eigenfaces for Recognition
Authors: Turk Matthew , Pentland Alex 
Published: February 2008

Abstract
We have developed a near-real-time computer system that can locate and track a subject's head, and then recognize the person by comparing characteristics of the face to those of known individuals. The computational approach taken in this system is motivated by both physiology and information theory, as well as by the practical requirements of near-real-time performance and accuracy. Our approach treats the face recognition problem as an intrinsically two-dimensional (2-D) recognition problem rather than requiring recovery of three-dimensional geometry, taking advantage of the fact that faces are normally upright and thus may be described by a small set of 2-D characteristic views. The system functions by projecting face images onto a feature space that spans the significant variations among known face images. The significant features are known as "eigenfaces," because they are the eigenvectors (principal components) of the set of faces; they do not necessarily correspond to features such as eyes, ears, and noses. The projection operation characterizes an individual face by a weighted sum of the eigenface features, and so to recognize a particular face it is necessary only to compare these weights to those of known individuals. Some particular advantages of our approach are that it provides for the ability to learn and later recognize new faces in an unsupervised manner, and that it is easy to implement using a neural network architecture.
Visual Processing of Faces in Temporal Cortex: Physiological Evidence for a Modular Organization and Possible Anatomical Correlates
Authors: Harries M. H. , Perrett D. I. 
Published: February 2008

Abstract
Physiological recordings along the length of the upper bank of the superior temporal sulcus (STS) revealed cells each of which was selectively responsive to a particular view of the head and body. Such cells were grouped in large patches 3-4 mm across. The patches were separated by regions of cortex containing cells responsive to other stimuli. The distribution of cells projecting from temporal cortex to the posterior regions of the inferior parietal lobe was studied with retrogradely transported fluorescent dyes. A strong temporoparietal projection was found originating from the upper bank of the STS. Cells projecting to the parietal cortex occurred in large patches or bands. The size and periodicity of modules defined through anatomical connections matched the functional subdivisions of the STS cortex involved in face processing evident in physiological recordings. It is speculated that the temporoparietal projections could provide a route through which temporal lobe analysis of facial signals about the direction of others' attention can be passed to parietal systems concerned with spatial awareness.