Sensation & Perception : Anatomy of the Brain

Cerebral Cortex, Limbic System

What are the parts of the forebrain?

Limbic system function

Controls mood & attitude

Stores highly charged emotional memories

Controls appetite and sleep cycles

Anatomy of the Limbic System

Amygdala

Hippocampus

Thalamus

Hypothalamus

Amygdala

Anger & fear

Hippocampus

Important for memories

Thalamus

Relay sensory info to cerebral cortex

Hypothalamus

Important for metabolic behaviors

- Eating, drinking, sexual behaviors, & emotions

midbrain

Extends from pons to lower thalamus

Reticular Activating System

Controls :

- Respiration

- Cardiovascular function

- Digestion

- Alertness

- Sleep

Brain Stem

Vital in basic attention, arousal, & consciousness

Superior Colliculi

Vision

Inferior Colliculi

Hearing

Medulla Oblongata, Pons, Cerebellum

What are the parts of the hindbrain?

Medulla Oblongata

Breathing, swallowing, & digestion

Pons

Relay station

Cerebellum

Motor coordination, posture & maintaining balance

Contra-laterality

Control of one side of your body by the other side of your brain

Right Side of Brain => ___________

Controls left side of body

Left Side of Brain => ___________

Controls right side of body

Corpus Callosum

Neural fibers connecting left & right lobes

Allows communication between right & left sides of the brain

Wernicke's Area

Speaks fluently, but nonsensically

Not coherent, contains lexical & grammatical errors

Broca's Area

Can understand everything said

Patient can only respond in monosyllabic words

Sensory Code

Representation of perceived objects through neural firing

Specificity Coding

Specific neurons respond to specific stimuli

- Leads to "grandmother cell" hypothesis

Problems with Specificity Coding

Too many different stimuli to assign specific neurons

Most neurons respond to number of different stimuli

Distributed Coding

Patters of firing across many neurons, codes specific objects

- Large number of stimuli can be coded by a few neurons

Sparse Coding

Only small number of neurons needed for an object

- Midpoints between Specificity & Distributed Coding

Occipital Lobe, Extrastriate Cortex, Tertiary Visual Cortex

What are the parts of the visual cortex?

Occipital Lobe

Primary Visual Cortex, Striate Cortex

- V1 => Area 17

Extrastriate Cortex

Secondary Visual Cortex

- V2 => Area 18

- V3 => Area 19

Tertiary Visual Cortex

Parietal Lobe

Temporal Lobe

Simple Cell Neuron

- Responsive to bar of light

- Excitatory

- Inhibitory

- Orientation Tuning Curve

Complex Cells

Larger receptive field

Responsiveness to a certain direction of motion

End-Stopped Cells

Hypercomplex cells

- Responsive to orientation and direction of motion & length, width, or other features

Ex.) Corner

Ganglion Cells

1 million

- Convergence from rods & cones

Parvo Cells

Magno Cells

Parvo Cells

Small, 20m/sec

Detailed form analysis, spatial analysis, color vision

Magno Cells (y cells)

Large, rapid conduction rate

Motion detection, temporal analysis, depth perception

LGN (Lateral Geniculate Nucleus)

Kidney-bean shaped structure in thalamus

6 Layers

Layer II, III, IV b

Blobs, interblobs

Layer IV b

Orientation & movement

Layer V

Direction of movement

Layer VI

Directionally sensitive

Orientation Column

IV b, Interblobs

- Cells sensitive to various orientations are aligned in a column

Ocular Dominance Column

Organized in terms of eye

- Preferential response to one eye

- Systematically arranged in alternating stripes across the cortex (.25 - .5mm)

Hype-Column

Processing module

1 mm block

Left & Right

- 0 - 180 degrees

Magnification Factor

Fovea is .01% of retina, but 8% of neurons in striate cortex

Ventral Pathway

Temporal Lobe

Visual Agnosia

Prosopagnosia

Temporal Lobe

"What" area

- V4 => Color

- IT (Inferotemporal Area) : Form & Face perception

Visual Agnosia

Can't recognize object

Prosopagnosia

Can't recognize familiar faces

- FFA in fusiform gyrus

Fusiform Face Area (FFA)

Responds best to faces

Parahippocampal Place Area (PPA)

Responds best to spatial layout

Extrastriate Body Area (EBA)

Responds best to pictures of full bodies & body parts

Dorsal Pathway

Parietal Lobe

MT (Medial Temporal Lobe)

Parietal Lobe

"Where" & "How" area

Lesion => Difficulty learning to respond on the basis of relative spatial location

Medial Temporal Lobe (MT)

Motion Perception

Motion Agnosia

- Akinetopsia

Ganal Experiment

Designed to demonstrate a separation of perception and action in non-brain damaged subjects

Greebles Experiment

Bird-like artificial figures

- FFA responded after training to Greebles