behavioral neuroscience exam 3

reflexes

automatic, involuntary responses to specific stimuli; involve direct sensory-motor neuron pathways

Motor plans

Pre-programmed sets of movements that the brain organizes before execution

Movements

Individual muscle contractions

Acts

Coordinated actions

EMG

Measures the electrical activity in muscles

Lesion Studies

researchers study what happens when a specific part of the brain is damaged

Brain Imaging

Uses special machines to see which parts of the brain are active OR what they look like (MRI and fMRI)

Hierarchy of motor control

Muscles —> Spinal Cord —> brainstem —> primary motor cortex —> nonprimary areas; controls reflexes to complex voluntary actions

Primary motor cortex (M1)

Initiates voluntary movements; located in precentral gyrus

Nonprimary motor cortex

Includes premotor and supplementary areas that plan and sequence complex actions

Muscle Spindles

Sensory receptors detecting muscle strength; provide feedback for reflexive contraction

Golgi tendon organs

detect muscle tension and prevent over-contraction by inhibiting excessive force

Sensory feedback loop

Muscle spindles and golgi tendon organs constantly provide information to fine-tune movement

Neuromuscular Junction

Synapse where motor neurons release acetylcholine to activate muscle fibers and cause contraction

Acetylcholine

neurotransmitter used at the NMJ to inititate muscle contractions

Myasthenia Gravis

Disorder where ACh receptors are attacked, causing muscle weekness

Pyramidal tract

motor pathway from M1 through medulla to spinal cord; controls voluntary, precise movements

Extrapyramidal system

includes basal ganglia, cerebellum, and brainstem pathways that regulate coordination, tone, and posture

Parkinson’s disease

loss of dopamine in the substantia nigra; causes tremors, rigidity, and slowed movements

Huntington’s disease

Degeneration of the basal ganglia causing involuntary, jerky movements

Cerebellar damage

leads to ataxia (poor coordination and balance)

Motor cortex damage

Can cause paralysis or apraxia (inability to plan movements)

Sensory transduction

process of converting physical stimuli (light, sound, touch) into neural signals

neural coding 

how the brain represents stimulus type, intensity, and location through neural firing patterns

generator potentials

local graded potentials in receptor cells that can trigger action potentials

receptive field

specific region or stimulus type a neuron responds to; critical for spatial encoding

center-surround organization

pattern in receptive fields (esp. vision) that enhances contrast and edge detection

sensory adaptation

decreased receptor sensitivity after constant stimulation

hierarchy of sensory processing

receptor—> spinal cord/brainstem—> thalamus —> primary sensory cortex—> association cortex

cornea and lens

focus light

retina 

contains photoreceptors

optic disc

the blind spot

fovea

provides sharp vision

Rods

Photoreceptors for dim light and motion; located in the periphery of the retina

Cones

Photoreceptors for color and detail; concentration in the fovea

Photopic vision

cone-based, bright light

Scotopic

rod-based, low light

visual pathway

retina—>optic nerve—>optic chiasm—> LGN (thalamus)—>primary visual cortex (V1)—> higher areas

Lateral geniculate nucleus

Thalamic relay center for visual information; organizes input before it reaches the cortex

primary visual cortex

processes orientation, edges, and spatial detail from the LGN

Light transduction process

1. Light activates photopigments (rhodopsin)

2. Photoreceptors hyperpolarize

3. Signal passes to bipolar—>ganglion cells—>brain

4. Light decreases neurotransmitter release (unlike most systems)

Receptive fields in vision

retinal ganglion and LGN cells have center-surround fields; cortical cells detect edges, orientation, and motion

simple cells (V1)

respond to specific orientations of edges or lines

complex cells (V1)

respond to motion and direction of visual stimuli

dorsal stream

the “where/how” pathway; processes motion and spatial location; goes from V1 to parietal lobe

Ventral stream

“what” pathway; processes object recognition, color, and form; goes from V1 to temporal lobe

optic ataxia

damage to dorsal stream; difficulty using visual information to guide movements

visual agnosia

damage to ventral stream; inability to recognize object