L7 Sleep, Decision-Making Flashcards
Circadian cycle
evolved to maintain appropriate daily rhythms and hmeostatic functions with variable daylight in variable seasons
Cells of Circadian Cycle
Photosensitive ganglion cells that detect the cues for the clock
contain photopigment called melanopsin and are depolarized by light
help to encode illumination, allow for reset of circadian clock
project to the suprachiasmatic nucleus (SCN), which controls the circadian cycle
Melatonin
produced by the pineal gland
modulates neural activity by activating melatonin receptors on neurons in SCN
Orexin
promotes wakefulness, from the hypothalamus
Suprachiasmatic nucleus
governs physiologic responses associated with sleep wake cycle including BP, hormone secretion, body temp, urine output
Even with light cues removed…
individuals present with a 24 hour clock
Sleep
defined behaviorally by the normal suspension of consciousness and electrophysiologically by specific wave critera
Sleep deprivation
can be deleterious and even fatal
can also call mood swings, hallucinations
Sleep is not just a downregulation of brain activity…
series of precisely controlled physiological states governed by brainstem nuclei
high levels of brain activity occurs
Amount of sleep required
Adults: 7-8
Teens: 9
Babies: more
Sleep debt
getting too little sleep that has to be made up
judgement, reaction time, memory, cognitive, other functions are impaired
What are the purposes of sleep?
- Energy conservation
- Memory Consolidation
- Metabolic wastes cleared from brain
- We are dependent on visual info to find food, need to avoid predators
Energy conservation and sleep
sleep replenishes brain glycogen levels
minimize heat loss by dropping body temp
metabolism is decreased during slep
Fatal Familial Insomnia
Genetic disorder that causes death within several years of onset, unable to enter REM sleep
Stage 2 Sleep
further decrease in frequency of EEG waves and increase in the amplitude, also has high frequency spike clusters called sleep spindles
Stages of Sleep
defined by the amount of electroencephalographic energy recorded
Stage 1 Sleep
Drowsy period
decrease in EEG frequency, increased amplitude
Sleep Spindles
periodic bursts of activity at about 10 to 12 Hz that generally last 1 to 2 seconds and arise as a result of interactions between thalamic and cortical neurons
Stage 3 Sleep
moderate to deep sleep
number of sleep spindles decreases
amplitude of EEG increases, frequency decreases
Stage 4 Sleep
deepest level of sleep
low level of EEG frequency, high amplitude fluctuations (delta waves)
takes about an hour to reach this stage
Slow wave cycle
Stage 3 and Stage 4
Non-REM sleep
Stages 1-4
REM Sleep
EEG recordings are similar to as when you are awake
after about 10 minutes in REM, the brain cycles to the other 4 stages
about 4 periods of REM sleep occur
Stage 1 Physiological Changes
slow, rolling eye movements
decrease in muscle tone, body movements, heart rate, breathing, BP, metabolic rate, temperature
(reach their lowest values in stage 4)
REM Sleep Physiological Changes
increases in BP, HR, metabolism
rapid ballistic eye movements, pupillary constriction, paralysis, twitching of smaller muscles
Dreams occur during REM
sleep walking and sleep talking do not occur in REM, are not motivated by dreams
Prefrontal Cortex of Frontal Lobe
helps with decision-making/thinking/planning
difficult to identify the flow of information through the PFC
Rough Path of input to output in prefrontal cortex
- Info about sensory stimuli is conveyed to orbitofrontal cortex
- This info flows rostrally and laterally to other lateral and medial PFC
- Then the resulting signals flow to other PFC regions that use info to plan possible responses
- Signals are sent to premotor and parietal cortexes, then other cortical regions that help with behavior, which are influenced by dopamine, serotonin
Orbitofrontal Cortex
-OFC receives input from all major modalities, has few motor connections
-Receives input from hippocampus and m. temporal lobe (memory storage and retrieval)
-Input from reward related dopamine neurons in midbrain
OFC output
-OFC provides output to systems that help with selection and execution of behaviors
OFC Purpose
-helps us to perform estimation of the value of an option based on past and present information
-helps shape associations among objects, actions, consequences
-integrates info about prior experiences to help determine value of different choices
-subjective value: value can change with other sensory inputs, like fullness
Common currency theory
the OFC and the ventromedial prefrontal cortex make use of a universal value that allows comparison of any decision
Actually making a choice
occurs after evaluation and requires values of each of the options
the vmPFC and the OFC show systematic changes when the values of multiple options are maintained
Lesions of the vmPFC
deficits in comparing values of different options
buying a car–the individual wouldn’t be able to figure out between price, styling, mileage, etc
Dorsolateral Prefrontal Cortex
- Communicates with reward related regions like the OFC and anterior cingulate cortex, premotor cortex, parietal areas
- Changes in firing rate are matched with changes in rules that govern effective behavior
Damage: when the rule is changed, individuals continue with the one that they learned. Impairments of short term memory
Cingulate Cortex
- Might be the source of error-related negativity
- Concerned with consequences of choosing an option than by the nature of the option or its value
- Helps us to learn from our consequences
- Generation of feedback signals that help to update goals and adapt new rules
- Detects the need to change
- Helps with conflicting action plans that are activated at the same time
Error-related negativity
observed in standard lab tasks immediately after an individual commits an error, changes in levels of dopamine when an error is committed
Cingulate Cortex lesions
lead to impairments in learning from consequences of actions
OCD
associated with atypical levels of activity in the anterior cingulate cortex
overly sensitive to stimuli
self-doubt
Illogical acts
Ventrolateral Prefrontal Cortex
- Self-control
- Damage to this area causes impulsivity. Tourettes, OCD, depression are examples
Anterior Insula
- Uses body stats to regulate behavior
- Associated with emotional awareness and expression. Attention, love, time perception, music
- Can play a role in gambling and drug addiction
Posterior Cingulate Cortex
- Self-Awareness
- Has slow long lasting fluctuations with reduced activity during performance of tasks, high activity between trials
- Not exactly clear as to what the role is, possibly involved in default mode network
- Active during daydreaming, distracted
- Info about self, like autobiographical memory, thinking about your future, considering others in relatin to yourself
Damage: Alzheimer’s disease
