Brain And Behavior 2: Executive Circuits And Memory/emotion

Question 1

How is sensory input filtered/sharpened?

Answer 1

Through reciprocal connections

Ex: cortex -> thalamus and thalamus -> cortex

pathological states in these reciprocal connections can cause “false signals or inappropriate suppression of sensations”.

Question 2

Function of the parietal association cortex

Answer 2

Sensory guidance of motor behavior and spatial awareness

Question 3

Temporal association cortex function

Answer 3

Recognition of sensory stimuli and storage of semantic knowledge (facts)

Question 4

Frontal association cortex function

Answer 4

Organizing behavior and working memory

Question 5

Limbic association cortex function

Answer 5

Complex functions related to emotion and episodic memory

Question 6

Attention vs impulsivity

Answer 6

Both are opposites, but controlled by the nucleus accumbens and ventral tegmental areas in the limbic system

• increased release of dopamine -> increased pleasure and attention to that action
• decreased or no release of dopamine -> no increased pleasure and hypersensitivity to impulsive stimuli

*because of this, dopamine stimulant medications are used for ADHD patients since they are now able to block out irrelevant stimuli easier and focus on one stimuli since the dopamine medication makes them feel “pleasure” to that one stimuli by increasing dopamine release in the nucleus accumbens *

Question 7

Types of declarative/explicit long term memory

Answer 7

Episodic memory
- events/ scenes

Semantic memory
- facts/semantics

both take place in hippocampus and associated cortical areas

Question 8

Types of non declarative/implicit memory

Answer 8

Skills

Habits

Emotional memories

Conditioned reflexes

all are controlled by the cerebellum, basal ganglia, amygdala and associated cortical areas

Question 9

Working memory

Answer 9

Describes what is being actively considered at the time or within a few seconds

Involves the hippocampus and prefrontal cortex

Modulated by dopamine and norepinephrine neurotransmitters

• dopamine antagonists result in decreased/delayed working memory (haloperidol)
• dopamine and NE agonists enhance working memory and improve attention

impaired working memory = ADHD and schizophrenia

Question 10

ADHD pharmacological treatments

Answer 10

Dextroamphetamine or methylphenidate

- increase dopaminergic signaling via agonists of dopamine neurons

Question 11

Transition of short-term -> long-term memory

Answer 11

Experiences enter the brain through senses and processed by respective cortexes

Processed information goes to the hippocampus and is assigned emotional importance via amygdala if possible
- more emotional response assigned = more permanent and/or easier to recall

Then is stored in the specific cortex again as long term memory
- this action is thought to occur during sleep (so getting good sleep = better long term memory)

Question 12

Declarative memory

Answer 12

Thought to be physically contained in medial temporal and midline diencephalic structures and in the neocortex

Contains episodic and semantic memories

Question 13

Nondeclarative memory

Answer 13

Skills and habits

Dependent on the neocortex and neostriatum

Cerebellum is highly important for nondeclarative memories associated with muscles specifically

Amygdala is highly important for emotional learning assigned to nondeclarative memories

Question 14

Anterograde vs retrograde amnesias

Answer 14

Anterograde = can remember past but cant form new memories
- is believed to occur if the hippocampus or amygdala are lesioned

Retrograde = cant remember past memories but can make new memories

Question 15

Feelings vs emotions

Answer 15

Emotion = set of physiological responses that occur more or less unconsciously when the brain encounters challenging situations

Feelings = conscious experience of these semantic and cognitive changes

Question 16

How are emotional responses generated for external stimuli?

Answer 16

1) External stimuli are processed by their specific cortexes
2) the processed info (if emotionally salient) is then sent to the amygdala to attach emotional responses to the external stimuli

3) info is then sent out to the hypothalamus and brain stem to effector cells for actions to be tied to the external stimuli. Includes:
- pituitary and endocrine glands (increase cortisol if “stressed”)
- somatic motor nerves and skeletal muscles (freezes or flees)
- Autonomic nerves and smooth/cardiac muscles (increases or decreases HR/BP/BR)

note direct electrical stimuli to the hypothalamus induces “fight or flight responses subconciously

Question 17

Aggression and serotonin levels

Answer 17

Indirectly proportional to each other.

Low serotonin metabolite levels (5-HIAA) are associated with increased aggressive behavior and greater suicidal ideologies, as well as increased odds of lethality in suicide attempts.

Acute tryptophan (precursor for serotonin) deficiencies = increased irritability and aggression

Question 18

Theories surrounding the concept of feelings

Answer 18

Peripheral feedback theory
- feelings are generated as a sensory feedback in response to an emotional stimulation in the bodies actions.

Central theory
- feelings are generated directly by the hypothalamus after it has evaluated emotional qualities of an external stimulus.

Papez circuit
- same thing as central but details more of the actual circuit used to conduct this

neural correlates in response to feelings supports hypothesis that feelings are correlated with activity in brain regions that monitor the body’s overall state.

Question 19

Hypothalamic-Pituitary- Adrenal axis (HPA)

Answer 19

Mediates the stress response in humans
- hypothalamus tells the pituitary to release ACTH into the circulation which then acts on adrenal glands to release cortisol into the blood stream which then mediates peripheral and CNS effects of “stress”

ACTH -> cortisol -> feelings of stressed out

patients with primary endocrine disorders (addisons, Cushings, hypo/hyperthyroid, etc) can present with psychiatric symptoms

Question 20

Effects of cortisol on the amygdala and hippocampus

Answer 20

Amygdala = prolonged stimulation - prolonged stress response
- improper emotional connection with external stimuli

Hippocampus = impairs stimulation

• impairs memory formation
• decreases neurogenesis and increases atrophy of the hippocampus
• disrupted long-term potentiation of neuronal pathways
• cant form long term memories
• increases depressive ideologies

Question 21

HPA axis in depression

Dexamethasone suppression test (DST)

Answer 21

HPA activity is increased in roughly 40-60% of all depressed patients

• increased cortisol levels are observes in almost all of these 40-60%
• also depressed individuals are associated with increased inflammation (feels fatigued and sick)

The laboratory test of use of dexamethasone to determine HPA axis activity and cortisol dysregulation can be used to help diagnosis depression

• normal patients = lower cortisol levels and suppression of the HPA axis
• depressed patients = no changes still dysregulated
• note that while DST is useful, it is limited since it often produces false positives as well as isnt specific to depression (others tests/ contains yield positive results for DST) *

Question 22

Cortisol and the immune system

Answer 22

Inverse relationship.

Increased cortisol levels suppress innate immunity

Also increased cytokine signals are received by the CNS causing feelings of fatigue

Question 23

Primary or secondary psychiatric disorders means what?

Answer 23

Primary = idiopathic or psychiatric cause

Secondary = organic cause due to endocrine hormone issues (hypothyroidism, cushings, Addisons, etc.)

Question 24

Learning vs memory

Answer 24

Learning = new information acquired by the nervous system which can be observed in the individual through behavioral changes

Memory = encoding, storage and retrieval of learned informations
* directly contributes to personality, habits and disposition unconsciously*

Question 25

Short term vs working memory

Answer 25

Working memory = what is being actively considered at the current time

• manipulates information to achieve an immediate goal
• (i.e: looking up a phone number and remembering it while actively dialing it)
• used for multitasking/calculations and reading
• there are no planning invitation or high level cognitive skills at work here (executive function)

Short-term memory = temporary, short term maintenance of information

• lasts a few minutes to days
• not quite long term
• often recalled for working memory