Neuropsychology

Neurophysiology of Perception:

Neurophysiology of Perception:

• Macroscopic view = large brain areas involved in perception

• Microscopic view = individual neurons and their activity

• Neurons communicate with action potentials (spikes)

• Visual cortex helps process visual information

Key idea: Perception depends on both brain regions and neuron firing.

The Neuron:

The Neuron:

• Receptor = detects a stimulus

• Signal becomes an electrical signal

• Dendrites = receive signals

• Cell body = processes them

• Axon = carries the signal away

• Synapse = passes the signal to the next neuron (gaps between terminal branches)

• Terminal branches = send signal to the next neuron

Stimulus → receptor → dendrite → cell body → axon → terminal branches → synapse

Electrical Potential of a Neuron:

Electrical Potential of a Neuron:

• At rest: -70 mV

• More K⁺ inside, more Na⁺ outside

• Sodium-potassium pump maintains this balance

• When neuron fires: Na⁺ rushes in

• Voltage rises to about +40 mV

• Then K⁺ flows out

• Neuron returns to -70 mV

Rest (-70) → Na⁺ in → +40 → K⁺ out → Rest (-70)

Action Potential:

Action Potential:

• Action potential = neuron’s main electrical signal

• Very fast: about 1 millisecond

• Na⁺ enters → voltage rises

• K⁺ leaves → voltage returns to rest

• Neurons can fire up to about 1000 times/second

Na⁺ in → neuron fires → K⁺ out → reset

Synapse:

Synapse:

• Synapse = gap between two neurons

• Usually between terminal branches of one neuron and dendrites of the next

• Presynaptic neuron = sends the signal

• Postsynaptic neuron = receives the signal

• Action potential reaches terminal → neurotransmitters are released

• Neurotransmitters cross synapse and bind to receptors

Action potential → neurotransmitter release → crosses synapse → binds next neuron

Neurotransmitters:

Neurotransmitters:

• Neurotransmitters can excite or inhibit neurons

• Excitatory NT → increases firing

• Inhibitory NT → decreases firing

• The postsynaptic neuron adds up all excitatory + inhibitory signals

Excite = more firing
Inhibit = less firing

Single-Cell Neurophysiology:

Single-Cell Neurophysiology:

• Records the activity of one neuron

• A microelectrode measures the neuron’s firing

• Researchers test which stimulus makes the neuron fire most

• Neurons have preferred stimuli

• Receptive field = area where a stimulus affects that neuron

• Some neurons respond best to specific features, like vertical lines

• Hubel & Wiesel used this method to study vision

• Helped map how the visual cortex processes patterns

One neuron → test different stimuli → see what it responds to best