NEUR200 EXAM 3

rhythms

• biological rhythms tied to the passage of time

• circadian rhythm: 24 hour biological cycle influential in the regulation of sleep and other physical responses; the exposure to light readjusts people’s biological clocks by affecting the activity of the hypothalamus

hypothalamus

• SCN (suprachiasmatic nucleus)

  • influenced by light

  • controls the release of melatonin in the pineal gland (causes sleepiness)

  • light reaches the SCN directly in mammals (retinohypothalamic pathway)

reticular formation

• ascending fibers

• influence physiological arousal

locus coeruleus

• in the pons

• primary source of norepinephrine, regulating arousal, attention, stress responses, and memory

hypothalamus

• histamine: promotes wakefulness, arousal, and alertness by increasing neuronal activity in the cortex and inhibiting REM sleep

• orexin: needed to stay awake, inhibition of orexin can cause rats to fall asleep quickly > leads to narcolepsy

sleep stages, eeg

• stage 1: lasts 5 to 10 minutes (THETA WAVES)

• stage 2: brief bursts of higher-frequency brain waves

  • k-complex: sharp waves, temporal inhibition of neuronal firing. happen after sudden interruption in sleeping environment (like noise)

  • sleep spindles: generated in the thalamus, very brief 500 ms. more sleep spindles in people who napped, they were refreshed to do a learning task

• stage 3 and 4: slow-wave sleep; high amplitude, low frequency delta waves become prominent. synchronization of low-waves. reduction of sensory input

• stage 5 (REM SLEEP): rapid eye movement. high-frequency beta waves in some areas. dreams (happen during 3 and 4 too)

insomnia

• chronic problems in getting enough sleep

  • causes: anxiety, tension, depression

narcolepsy

• irresistible onsets of sleep during normal waking periods

  • causes: lack of hypothalamic cells that produce orexin, huntington’s (causes nerve cells in the brain to decay overtime)

sleep apnea

• frequent, reflexive gasping for air (of a minute) that awakens a person.

  • causes obesity, genetics, hormones, old-age deterioration of the brain mechanisms that regulate breathing

night terrors

• abrupt awakenings from NREM sleep accompanied by intense autonomic arousal and feelings of panic

nightmares

• anxiety-arousing dreams that lead to awakening

REM behavior disorder

• people who move around vigorously during their REM periods, acting out their dreams (caused by a GABA deficiency)

extra sleep disorders

• sleepwalking = motor cortex is awake

• lucid dreaming = monitoring areas are awake (frontal)

• waking up but not being able to move (sleep paralysis)

fatal familial insomnia

• inherited rare disease

• onset occurs when a critical amount of protein PrP is converted to PrPres

  • greater amounts of PrPres than normal in thalamus > degeneration of thalamus

• absence of sleep spindles and k-complexes

• deep sleep is reduced, REM sleep can happen during waking state

• weight loss, elevated sympathetic activation, hallucinations, epileptic seizures, coma, death

energy conservation

• sleep conserves energy during inefficient times

  • autonomic nervous system

  • analogous to hibernation

• differences across species

  • dishes that don’t sleep. they live in caves with no difference between day and night

  • humans have changed their sleep habits too (we used to sleep less i think idk)

sleep and memory (EEG)

• memories that are more important will be consolidated better during sleep

  • EEG patterns during sleep resemble those that occur during learning

  • sleep spindles increase in number after new learning

sleep and memory (learning and memory)

• the brain makes adjustments when we learn new things

  • strengthening new synapses

  • weakening or removing old synapses that are not used anymore

• reactivation process associated with consolidation begins when a memory is formed, but it becomes strong during sleep

  • steffan gais

    • high-school students had to learn a list of 24 pairs english-german words

    • the “sleep” group went to sleep after learning the words (~3 hours max)

    • the “awake” group didn’t go to sleep until ~10 hours after learning the words

    • people who didn’t sleep were found to forget more

attention

• narrowing or focusing awareness selectively to a part of the sensory environment or to a class of stimuli

  • primarily a top-down process that selects information from a specific part of the sensory world, such as a point in space or an object

consciousness

• is synonymous at a primary level with awareness and at a secondary level with awareness of awareness (first person experience of the events that you are aware of)

  • consciousness is not that selective, it summarizes all information pertinent to the individual and its environmen

fmri findings

• parietal cortex is needed for attention to location

• occipital and temporal lobes are more important for feature

• the anterior cingulate and prefrontal areas are important for both, attention to location and features, mainly in divided attention tasks

  • when subjects attend only to auditory or visual stimuli, there is an activation of sensory areas, but not much activation of the frontal lobe. to attend to both modalities, simultaneously requires a recruitment of the dorsolateral prefrontal cortex

alerting network

• reticular activating system (RAS) >

• locus coeruleus (noradrenaline) >

• acts to prepare regions (alertness), especially in prefrontal and posterior parietal cortex, for detecting stimuli rapidly

orienting network

• acetylcholine

• prioritizes sensory input by selecting a sensory modality or a location in space

dorsal attention system

• top-down visuospatial

• right-lateralized (neglect syndrome, opposite side of the body)

• fronto-parietal executive networks (DLPFC)

default mode network

• thinking about one’s past, thinking about the future, or mind wandering (mPFC, PCC, medial temporal areas)

salience network

• most active when a behavioral change is needed. if the salience network is not functioning properly, the default network shows excessive activity, leading to lapses in attention (ACC, insula)

dual executive networks

• frontoparietal network

  • thought to relate to task instructions that are transient at the beginning of a new task

• cingulo-opercular network

  • sustained activity across the task

synchrony

• the attentional system induces synchrony across a population of neurons that assess some sensory light

  • importance of temporal positions of action potentials > ie several inputs to a given neuron arrive together

• increasing activity in the attention network increases brain synchrony globally

• increasing activity in the default network may have the opposite affect - a loss of global synchrony

meditation

• meditation reduces activity in DMN and increases in salience and central executive network connectivity

• increased activity of anterior cingulate during mediation

working memory

• may be two working memory (short-term) systems for spatial and object memory

• dorsal and ventral visual pathways from the parietal cortex and from the temporal lobes project to different prefrontal cortical regions and support two kinds of short-term memory

  • the dorsal stream enable vision for action and the ventral stream, vision for perception

encoding

• sensory system to STM

• visual objects: right prefrontal and right parahippocampal cortez

• words: left prefrontal and parahippocampal cortex

consolidation

• into LTM: medial temporal lobe

• after further processig that involves the hippocampus, the permanent memory storage may require the outermost layer of the cortex, layer 1, which has few neuronal cell bodies but is packed with synapses

• engrams: WHAT pathway (visual cortex for visual objects, auditory cortex for auditory objects)

retrieval

• requires attention (frontal areas)

• retrieval from LTM makes the memories plastic again and they can be updated - importance for PTSD therapy

long term memory

… pic

long-term explicit memory: episodic memory

memory of life experiences centered on the person herself

long-term explicit memory: semantic memory

knowledge about the world - nonautobiographical knowledge. ie ability to recognize family, friends, information learned in school

neural substrates

• temporal-frontal-lobes

• ventral stream

• temporal lobe: hippocampus and rhinal cortex mainly

• acetylcholine, serotonin, and noradrenaline

long-term memory and hippocampus

• explicit memory, specifically episodic

• spatial memory; morris water maze (rodents)

  • hippocampus as a spatial map

  • london taxi drivers; hippocampus activates more when they answer to spatial questions

contextual memory

• the hippocampus brings together representations from various locations and reconstructs the context

long-term implicit memory: fear conditioning, amygdala

• damage to the amygdala abolishes emotional memory but has little effect on other types of implicit or explicit memory

long-term implicit memory: procedural learning, basal ganglia

• people with parkinson’s disease may have problems with this type of memory

procedural memory and basal ganglia

• striatum, globus pallidus, substantia nigra

• gradual learning of habits

• reinforcement-based teaching (trial and error)

• related to procedural memory

• this type of learning is less flexible

• you may need your frontal cortex at the beginning, otherwise it takes a long time to learn

  • prefrontal cortex: it is more flexible, switching responses

long-term potentiation

• Glutamate receptors: AMPA and NMDA. NMDA receptors are blocked by Magnesium (positive ions). They open after depolarization.

• When Calcium (together with sodium) enters through the NMDA channels, it will lead to the release of the protein CREB, that goes to the nucleus and alters genes (gene expression) that can last for months or years.

• These effects are modulated by the brain-derived neurotrophic factor (BDNF): Repeated activation will lead to action potentials that back- propagate into dendrites and release BDNF. BDNF can increase NMDA receptor activity.

anterograde amnesia

• disruption of memory for experiences after the onset of amnesia

retrograde amnesia

• disrupt memory for things learned prior to the event that initiated the amnesia

time-dependent retrograde amnesia

• injury severity determines how far back in time the amnesia extends. people usually start remembering with the passage of time and they only end up with an amnesia of a few seconds to minutes for events preceding the injury

amnesia (HM patient)

• henry molaison, removed his hippocampus to end with his epilepsy

• suffered with anterograde and retrograde amnesia

• severe impairment of episodic memory (he could not describe any event that happened after his surgery)

• Also, people with amnesia are as impaired at imagining the future as they are at describing the past → Function of episodic memory.

• Better implicit than explicit memory.

• Intact WM, but as soon as he was distracted, the memory was gone within seconds → Impaired storage of LTM (i.e. he was 27 for the rest of his life).

• Intact procedural memory (i.e. videogames).

broca’s area

• inferior frontal gyrus (44 and 45 of broadmann’s)

wernike’s area

• superior temporal hyrus (22 of broadmann’s)

heschl’s gyrus

• primary auditory cortex (41 and 42)

premotor area 6

• facial movements (mirror neurons)

• the dorsal part of area 6 (SMA) is important for rhythmic mouth movements that articulate sounds

visual areas

• left fusiform cortex (important for reading)

• cerebellum

wernicke

• poor comprehension

• paraphasias (the production of unintended syllables, words or phrases during speech ie “pike” instead of “pipe” and anomias

• fluent speech and poor repetition

transcortical (sensory)

• extrasylvian regions (POT junction)

• poor comprehension, paraphasias and anomias

• fluent speech and good repetition