Class 2, Lecture 3, Chapter 2: The Neural Basis for Cognition
The Primary Motor Area of the brain is adjacent to the primary sensory area of the
The visual system
Vision is the modality through which much of our knowledge is acquired
vision provides an excellent illustration for how the close study of the brain can
proceed, and what it can teach us.
The structure of the eye is designed to project a sharp image onto the retina, the light-
sensitive tissue that lines the back of the eye.
o For cognition, we are mainly concerned with the retina and the cells that start
the cognitive process once light it received.
Two types of photoreceptors, or cells that respond to light, are found on the retina
Lower acuity low detail detection, very grainy, not very fine
Found in periphery of the retina
Higher acuity able to perceive detail, much more densely packed.
Found in the fovea
A series of neurons communicates information from the retina to the cortex
o In the eye
Bipolar Cells Ganglion cells and the optic nerve (which has direct connection to the
o In the thalamus
Lateral geniculate nucleus (LGN)
o In the cortex
V1, the primary visual projection area, or primary visual cortex,
located in the occipital lobe
Visual processing and analysis begins in the retina.
Patterns of lateral inhibition between neighboring cells of the retina
leads to edge enhancement.
o Lateral inhibition links
o Basically what happens is the cells in the retina
transfer activation when a dark patch is next to a
bright patch, only occurs when there is light
next to dark.
o The bright patch gets bright, the dark patch
darker projects a lighter projection
experience to the viewer (increasing the activation in lighter areas) and decreases the
activation in darker areas
o Much of what we know about the visual system comes from a technique
known as single-cell recording.
o To understand this technique, we need to learn a few things about neurons.
o The basic parts of a neuron are:
Dendrites, which detect incoming signals
The cell body, which contains the nucleus
and cellular machinery
The axon, which transmits signals to other neurons
o Communication between neurons is done via chemical signals
Neurotransmitters are chemicals released by one neuron to
communicate with another neuron.
The space between the two is called a synapse.
Thus, the first neuron is called the presynaptic neuron and the second
neuron the postsynaptic neuron.
o Communication within neurons is done via electrical signals.
Neurotransmitters affect the post-synaptic neuron by changing ion
distributions and resulting electrical potentials.
If the post-synaptic cell reaches threshold, an action potential is fired
and propagates down the axon, releasing neurotransmitter that affects
the next neuron.
It is the notion of THRESHOLD that is important for our purposes
In order for us to recognize things w