Organization of the Nervous System

PSY 327- QUIZ #2

What is the simple linear model of behavior

→ Input → processing → output.

Why is input → processing → output insufficient?

It cannot fully explain flexible, real-time behavior.

In the ball example, what is the visual input?

seeing the ball

In the ball example, what happens during processing?

The nervous system computes where to move.

In the ball example, what is the motor output?

Moving the hand

What sequence better describes the process of responding to the ball

Predict → act → feedback → update.

Why is prediction important in real-time behavior?

The nervous system must anticipate what will happen rather than simply wait for input and respond afterward.

What is one major problem with a simple linear model?

It ignores parallel processing.

What is parallel processing?

Multiple processes can occur at the same time rather than one after another in a simple sequence.

What important influences does a simple linear model lack?

Feedback and context.

Why is feedback important for behavior?

It provides information that allows behavior to be updated or corrected.

Why can't simple linear models explain flexible adjustment?

They treat behavior as a one-way sequence rather than something that is continuously modified.

How does complex behavior actually emerge?

Through parallel, recurrent processing with continuous feedback and updating.

What does recurrent processing mean in the context of these notes?

Information is continuously fed back and used to update ongoing processing rather than simply moving in one direction.

What is the major contrast between a linear model and the model supported by the notes?

• Linear: input → processing → output.

• Better model: continuous, parallel processing involving feedback and updating

what conclusions were made about the ventricular brain image?

• Behavior cannot be mapped simply onto the amount of brain tissue

• functions emerge from distirbuted and interacting neural systems

• Yet brain regions are not interchangeable; different levels and regions make different contributions 

What behaviors can a spinal animal perform?

Reflexes only. It responds to appropriate sensory stimulation with stretching, withdrawal, support, scratching, paw shaking, etc.

What behaviors can a low decerebrate animal perform?

Postural support. When stimulated, it can perform units of movement such as hissing, biting, growling, chewing, lapping, and licking. It also shows exaggerated standing/postural reflexes and elements of sleepwalking behavior.

What behaviors can a high decerebrate animal perform?

Spontaneous movement. It responds to simple visual and auditory stimulation, performs automatic behaviors such as grooming, and can perform parts of voluntary movements when stimulated, such as standing, walking, turning, jumping, and climbing.

What behaviors can a diencephalic animal perform?

Affect and motivation. Voluntary movements occur spontaneously and excessively but are aimless. It shows well-integrated but poorly directed affective behavior and can thermoregulate effectively.

What behaviors can a decorticate animal perform?

Self-maintenance. It can link voluntary and automatic movements well enough for basic self-maintenance, such as eating and drinking, in a simple environment.

What does an animal with a typical/intact cortex gain?

Control and intention. It can perform organized sequences of voluntary movements, respond to patterns of sensory stimulation, form cognitive maps, understand relationships among objects/events/things, and add emotional value.

What is the overall pattern shown by this experiment?

As higher brain areas remain functional, behavior becomes increasingly complex:
reflexes → postural support → spontaneous movement → affect/motivation → self-maintenance → control/intention.

Match each highest remaining functional area with the major behavior it allows.

Spinal cord → Reflexes
Hindbrain → Postural support
Midbrain → Spontaneous movement
Hypothalamus/thalamus → Affect & motivation
Basal ganglia → Self-maintenance
Cortex → Control & intention

What is the difference between the functions of lower and higher levels of the nervous system?

Lower levels can independently produce basic reflexes and patterned movements, while higher levels integrate and coordinate these simpler functions to produce more complex, organized behavior.

true or false: higher levels do not replace lower ones, they modulate and organize them

true

what do added levels in the nervous system allow?

• Added levels allow behavior to incorporate motivation, context, planning, and intention

true or false: a simple action like grasping a cup recurits multiple levels of the nervous system?

true

why is visual information necessary in the nervous system?

visual information is required to locate target

what do frontal-lobe motor areas plan in the nervous system?

frontal-lobe motor areas plan the reach and command the movement

what does the spinal cord do during the action of grasping a coffee cup?

spinal cord carries information to hand

what do the motor neurons do in the process of grasping a coffee cup?

motor neurons carry message to muscles of the hand and forearm

what do the sensory receptors of the nervous system do when you’re grasping a coffee cup?

sensory receptors on the fingers send message to sensory cortex saying that the cup has been grasped

after the sensory receptors carry information, how does the spinal cord respond to grabbing the coffee cup?

spinal cord carries sensory information to the brain

what does the basal ganglia judge during the process fo grasping a coffee cup? the cerebullum?

basal ganglia judge grasp forces, and the cerebellum, corrects movement errors

After the basal ganglia judge, what does the sensory cortex do during the process of grasping a coffee cup?

sensory cortex receives the message that the cup has been grasped

in terms of senses and motor, how do the higher and lower levels of the nervous system compare?

• Higher levels contribute goals, planning, and adjustment

• Lower levels carry out and regulate movement and sensory processing 

true or false: noncontinuous sensory feedback allows the movement to be corrected as it unfolds

false: Continuous sensory feedback allows the movement to be corrected as it unfolds

what do classical reflex arcs handle?

classical reflex arcs handle fast, local responses

what do reflex arcs mediates but not explain?

reflex arcs mediate rapid automated responses but do not explain flexible voluntary behavior

what are the parts of the spinal cord and reflexes?

what is an example of the glabellar reflex?

Someone taps you on the forehead, and you automatically blink.

what is some examples of reflexes in babies?

• grasping reflex, babinski reflex (toes coming inward)

Do reflexes require cortical control?

No. Reflexes can be generated without cortical control.

what are reflexes?

rapid automatic responses to sensory input

Can the brain influence reflexes even though they do not require cortical control?

yes. Reflexes can be modulated or inhibited by descending signals from higher brain level

What is the role of local spinal circuits in reflexes?

They link sensory input → coordinated motor output.

Why can suppressed reflexes re-emerge after a CNS injury?

Higher-level control normally regulates/inhibits spinal reflex circuits. After CNS injury, that inhibition may be lost, allowing normally suppressed reflexes to re-emerge.

What are central pattern generators (CPGs)?

Neural circuits that generate rhythmic, patterned motor activity without needing a new voluntary command for every movement.

What are examples of movements controlled by central pattern generators?

Walking, breathing, and scratching.

How do higher brain systems control central pattern generators?

They can start, stop, and modify the movement pattern, such as walk → stop → speed up → step around a puddle.

What role does sensory feedback play in patterned movements?

Sensory feedback continuously fine-tunes the movement as it occurs.

what do higher brain regions do related to the CPG?

initiate, stop, and modify the pattern (e/g.m walk, change speed, step around an obstacle")

what do the spinal CPGs do?

produce a rhythmic pattern of motor output (e.g., alternating left-right)

what do motor neurons do?

motor neurons activate muscles, in a coordinated, repeating sequence

What is decussation?

The crossing of neural pathways from one side of the nervous system to the other.

Do all neural pathways cross over to the same degree?

→ No. The degree of crossing varies across different neural systems.

Because of decussation, which side of the body does each cerebral hemisphere primarily control?

The opposite side of the body.

What does contralateral control mean?

One side of the brain controls or receives information from the opposite side of the body.

• What does ipsilateral control mean?

• One side of the brain controls or receives information from the same side of the body.

• What is an example of contralateral control?

• The left cerebral hemisphere primarily controls the right side of the body, and vice versa.

• What is the key difference between contralateral and ipsilateral control?

Contralateral = opposite side; ipsilateral = same side

how does decussation work in term so vision?

• nasal retinal fibers cross from the optic chiasm

• each hemisphere process the opposite visual field

how does decussation work in term so hearing?

• auditory fibers cross (mainly in the brainstem, via the trapezoid body)

• each hemisphere processes more input form the opposite ear

how does decussation work in terms of balance (vestibular)?

• vestibular pathways project bilaterally with a major crossed component

• each hemisphere receives more input from the opposite side

where do fine touch, vibration, and proprioception cross?

• in the caudal medulla

what pathways carries fine touch, vibration, and proprioception?

the dorsal column-medial lemniscus pathway

where do pain, temperature, and crude touch cross?

in the spinal cord

what pathway carries pain, temperature and crude touch?

the spinothalamic tract

what side of the body does each hemisphere process somatosensory information from?

primarily the opposite (contralateral) side of the body

how does decussation work in terms of smell (olfaction)?

• does not decussate

• each olfactory bulb projects primarily to the same-side cortex (with some bilateral input)

how does decussation work in terms of taste (gustation)?

• taste fibers cross (via the brainstem, nucleus of the solitary tract)

• each hemisphere proceses more input from the opposite side of the tongue

Why is decussation considered a general principle rather than an absolute rule?

Because many neural pathways cross, but not all pathways cross in the same way or to the same degree.

What are the two main specialized cell types in the cortex?

Pyramidal neurons and interneurons.

Are pyramidal neurons primarily excitatory or inhibitory?

Primarily excitatory.

What type of connections do pyramidal neurons form?

Many long-range connections.

What is the major role of pyramidal neurons in the cortex?

 They are the major output neurons of the cortex.

Are interneurons primarily excitatory or inhibitory, and what connections do they form?

Primarily inhibitory and form mostly local connections.

What is the main function of interneurons?

They regulate activity within cortical circuits.

Where can the long-range outputs of pyramidal neurons project?

 To other cortical areas and subcortical structures.

What are examples of subcortical structures that pyramidal neurons can project to?

The thalamus and brainstem.