Cognitive Neuroscience Lecture 2: Neuroanatomy

**Neurons**—basic connectivity

Information
processing/signaling unit of the brain, basic element of computation

Folded makes
it closer together = faster connections

Blood
vessels bring nutrients

Noninvasive
neuroimaging measures oxygen levels in the brain

Grey matter:
mostly cell bodies

White
matter: mostly axons & fibres

Ventricles:
right, left, 3rd, 4th

Brain
has no skeleton, so fluid protects it from shock & pressure (offsets)

Contains
CSF

Three stages
of computation:

Receive signals from other cells (“input stage”):

o
Many
signals come in at dendrites

Process those inputs (“processing/evaluation stage”)

o
Signals
summate, adding and canceling, possibly reaching critical threshold within cell
body to send an output

Transmit signals to other cells (“output stage”)

o
If
the input is strong enough (exceeds threshold), then the neuron passes the
signal along via its axon

**Synapse**—where the axon of one neuron
connects to the dendrite of another neuron

Release of
neurotransmitter at the synapse

Pass signal
to post-synaptic neuron:

**Excitatory signals (EPSP)**—increase the probability that the
post-synaptic neuron will fire

**Inhibitory signals (IPSP)**—decrease the probability that the
post synaptic neuron will fire

Nervous
system is a “Chain of Neurons”

Sensory
Neurons (vision, touch, audition, taste, olfaction)à Interneurons à motor neurons (eye/body mvt)

Brain
hierarchy:

Neurons
(basic element of computation)

Brain
structures and areas (collections of neurons)

3 major
divisions of the brain:

**Cerebral cortex**—outer areas

**Limbic system**—inner structures

**Brain stem & cerebellum**—deep structures

Orientations

Dorsal
(superior) ßà Ventral (inferior)

Rostral
(anterior) ßà Caudal (posterior)

o
Spinal
cord: closer to head = rostral, closer to tail = caudal

Lateral
ßMedialàLateral

Cross
Sections

Transverse/horizontal—useful
for comparing anterior/posterior & right/left

Sagittal—useful
for comparing anterior/posterior & inferior/superior

Coronal—useful
for comparing  inferior/superior &
left/right

Dissection
shows that it’s not as easy to tell irl

Lobes

**Frontal**—high level functions

o
Reasoning,
planning, override and control of social responses, control parts of speech,
motor control, emotions, problem solving, executive control

**Parietal**—body/world interface

o
Somatosensation,
integrating sensory info across senses, spatial processing, attention, number
perception

**Temporal**—perception/memory interface

o
Auditory
sensation/perception, auditory recognition, visual recognition, long term
memory, speech production

**Occipital lobe**—Visual processing

Major Folds
(Sulci)

Sylvian
fissure (lateral sulcus)

Central
sulcus

Supramarginal

angular

Parieto-occipital
sulcus

Calcarine
fissure

Gyri

Frontal (superior, middle, inferior),
temporal 3 (superior,
middle, inferior), central 2

lateral occipital gyri

cingulate
gyrus

cuneate
gyrus

Subareas
within lobes: 52 Brodmann areas

Anatomically
subdividing regions of the cortex

Based
on cell architectonics: cell microanatomy

Brodmann
areas based on similarity/difference of cell architecture

52
regions

Subareas
within the lobes: functionally subdividing regions of the cortex

Picture
with PFC, orbitofrontal cortex, DLPFC, VLPFC, Frontal cortex, motor,
somatosensory, A1, V1

E.g.
subdividing frontal into prefrontal and motor

E.g.
sub region of parietal is somatosensory cortex

Basic
Organizing principle of the cortex: topographical mapping

Sensory/Motor
cortex has MAPS

Occipital
lobe: V1 = a map of *visual world* in
occipital cortex

o
**primary visual cortex**, Brodmann’s area 17, area 17, V1 all
refer to the same-ish place

o
**retinotopic** mapping in humans with fMRI:
position map

o
polar
angle map

o
eccentricity
map

Temporal:
A1 = a map of *sound* in auditory
cortex

o
near
Sylvian/lateral fissure: **A1** (**primary auditory cortex**)

o
**Tonotopic** map: frequency map

o
**Cortical tonotopy**: tone frequency MAP in A1

Parietal:
S1 = a map of the *body* in
somatosensory cortex

o
Electrical
stim of motor & somatosensory

o
Shows
map; homunculus

§  Disproportionate amount for hands
& face

Frontal:
M1 = another map of the *body* in motor
cortex

o
Electrical
stim shows map

o
Another
homunculus: also disproportionate amt for hands because detailed mvts

Do
other areas have maps? Maybe

**Limbic System: inner structures**

**Cingulate gyrus**

o
cognitive
control

o
error
detection

o
conflict
monitoring

**Thalamus**

o
relay
station for all of the senses

o
regulation
of sleep and arousal

**Hippocampus**

o
Long
term memory

o
Spatial
navigation

**Amygdala**

o
Emotion
processing

o
Memory
for emotive stimuli

Picture
of mid sagittal view of these and corpus callosum

**Brain stem & cerebellum: deep**
structures

**Cerebellum**

o
Most of brain’s neurons are here

o
Integrates
sensory and motor information

o
Maintain
balance of posture, walking, coordinate and time movements

o
Coordinate
muscle movements, motor control

o
Also
involved in some aspects of higher cognitive function; not sure what exactly

**Brain stem**

o
**Superior colliculus**: visual processing

o
**Inferior colliculus**: auditory processing

o
Colliculi
are for when an object comes flying at you, you want to get out of the way

o
**Medulla**:

§  Relay signals between brain &
spinal cord

§  Controls autonomic functions
(heart/blood pressure/respiration)

o
**Pons**:

§  Relays sensory information between
brain & cerebellum

§  Controls arousal

§  Important for sleep

Left
and right hemispheres connected by corpus callosum