Circadian Rhythms and Sleep

These flashcards cover key terms and concepts related to circadian rhythms, sleep, and memory, as discussed in the lecture notes.

Circadian Rhythms

Most physiological and biochemical processes in the body change across the day, displaying a rhythm of about 24 hours.

Zeitgeber

Any external cue that can synchronize the animal's endogenous rhythm, e.g., daylight.

Entrainment

The process of shifting/synchronizing the rhythm in accordance with the Zeitgeber.

Phase Shift

The shift in activity produced by the Zeitgeber; phase is a point in the cycle.

Suprachiasmatic Nucleus (SCN)

A tiny pair of neuron clusters in the hypothalamus responsible for regulating circadian rhythms.

Free-Running Period

The animal’s natural, endogenous rhythm, unaffected by external cues.

Activity Record (Actogram)

A visual representation of an organism's activity levels over time, used to study circadian rhythms.

Ultradian Rhythms

Biological rhythms that are shorter than one day, typically lasting minutes to hours.

Infradian Rhythms

Biological rhythms that are longer than one day, such as the menstrual cycle.

Jet Lag

A disorder of entrainment characterized by delay in the readjustment of the circadian pacemaker after rapid time-zone change.

REM Sleep

A stage of sleep characterized by rapid eye movement, vivid dreams, and muscle atonia.

SWS (Slow Wave Sleep)

A deep sleep state characterized by slow brain waves, during which physiological processes slow down.

Anhedonia

Inability to experience pleasure, often associated with mood disorders.

Cataplexy

Sudden loss of muscle tone without loss of consciousness, often triggered by strong emotional stimuli.

Cognitive Performance

The ability to utilize cognitive processes such as attention, memory, and learning.

Circannual Rhythms

Biological rhythms that are influenced by seasonal cycles, lasting approximately one year.

Declarative Memory

Type of long-term memory that involves the recollection of facts and experiences.

Nondeclarative (Procedural) Memory

Type of long-term memory that involves skills and tasks that can be performed and demonstrated.

Hippocampus

A brain region involved in the formation of new memories and is crucial for spatial memory.

Dopamine Hypothesis of Schizophrenia

Theory that schizophrenia is related to excessive levels of dopamine or sensitivity of dopamine receptors.

Dysthymia

A mild but long-term form of depression.

What are circadian rhythms?

Physiological and biochemical processes that change across the day, displaying a rhythm of about 24 hours.

What is an endogenous rhythm?

A natural rhythm generated internally by an organism, independent of external cues.

Who conducted the 1729 experiment related to circadian rhythms?

Jean Jacques d'Ortous de Mairan.

What is a Zeitgeber?

An external cue that can synchronize an organism's endogenous rhythm, such as light.

What is entrainment in the context of circadian rhythms?

The process of shifting or synchronizing the rhythm in accordance with a Zeitgeber.

What is a phase shift?

The shift in activity produced by a Zeitgeber, affecting the timing of the circadian rhythm.

What is the suprachiasmatic nucleus (SCN)?

A tiny pair of neuron clusters in the hypothalamus that regulates circadian rhythms.

What happens if the SCN is lesioned?

It causes arrhythmia, disrupting the normal circadian rhythm.

What is a free-running period?

The animal's natural, endogenous rhythm without external cues.

What is the significance of the tau mutation in hamsters?

It results in a free-running period of 22 hours, demonstrating genetic influence on circadian rhythms.

How does light affect the SCN?

Light information reaches the SCN via the retinohypothalamic pathway, entraining rhythms.

What role does the pineal gland play in circadian rhythms?

It releases melatonin, which is inhibited by signals from the SCN during the light phase.

What are ultradian rhythms?

Biological rhythms with periods shorter than 24 hours, such as those seen in feeding and hormone release.

What is jet lag?

A disorder of entrainment caused by rapid time-zone changes, leading to sleep disturbances and cognitive impairments.

What are some effects of circadian disorganization?

Impairments in cognitive performance, negative affect, headaches, and immune deficiency.

What is an actogram?

A visual representation of an organism's activity patterns over time, showing circadian rhythms.

What is the relationship between circadian rhythms and seasonal changes?

Circadian rhythms allow animals to synchronize their activity with seasonal changes in the environment.

What is the typical period of ultradian rhythms in humans?

90-110 minute cycles, such as in sleep and daydreaming.

What is the role of glutamate in circadian rhythms?

It allows light to entrain SCN activity rhythms.

How do SCN neurons influence other body systems?

They send projections to various brain areas and the pituitary gland, affecting hormone release and other rhythms.

What is the significance of reciprocal transplantation of SCN tissue?

It demonstrates that the SCN produces circadian rhythms, as the rhythm of the host matches that of the donor.

What is the effect of continuous darkness on a hamster's activity?

The hamster continues to show a daily rhythm, indicating an internal clock regulates its activity.

What is the impact of circadian rhythms on food acquisition in humans?

Humans have a diurnal rhythm that maximizes food acquisition during the day.

What is the relationship between brain size and ultradian rhythms?

The period of ultradian rhythms is correlated with brain and body size, with smaller animals having more rapid cycles.

What are infradian rhythms?

Biological rhythms that have periods greater than one day, such as the 28-day menstrual cycle.

What is a circannual rhythm?

A biological rhythm with a period of approximately 365 days, such as changes in body weight or reproductive behavior.

What is the role of the SCN in circannual rhythms?

The SCN does not consistently affect circannual rhythms in reproduction and body weight changes.

What is the typical human sleep cycle duration?

Adults typically go through four to five 90-110 minute sleep cycles each night.

What is the significance of REM sleep?

REM sleep is associated with dreaming and is characterized by rapid eye movement and muscle atonia.

How does sleep change across the lifespan?

Infants spend more time in REM sleep, while the elderly experience a decline in total sleep and stage 3 sleep.

What is sleep deprivation?

A condition that can lead to irritability, cognitive deficits, and in severe cases, compromise the immune system.

What is fatal familial insomnia?

A lethal condition associated with thalamic damage that prevents individuals from sleeping, typically onset in midlife.

What are sleep spindles?

Periodic bursts of 12-14 Hz brain waves that occur during sleep.

What is the delta rhythm?

Large amplitude, very low frequency waves that dominate stage 3 sleep (SWS).

What is the role of the basal forebrain in sleep?

It promotes slow-wave sleep (SWS) by releasing GABA into the tuberomammillary nucleus of the hypothalamus.

What triggers narcolepsy?

A mutation in the orexin receptor 2 gene, leading to inappropriate activation of REM sleep and atonia.

What is cataplexy?

A sudden loss of muscle tone without loss of consciousness, often triggered by emotional stimuli.

What happens during non-REM sleep?

Body temperature declines, heart rate decreases, and growth hormone release increases.

What is the difference between visual dreaming and thinking dreaming?

Visual dreaming occurs during REM sleep, while thinking dreaming occurs during non-REM sleep.

What is the function of the brainstem reticular formation?

It regulates wakefulness and sleep, with electrical stimulation leading to rapid awakening.

What is the impact of sleep deprivation on cognitive function?

Moderate sleep debt can lead to cognitive deficits comparable to those deprived for 3 days.

What is the role of delta waves during sleep?

Delta waves during stage 3 SWS may help flush out waste products from the brain.

What are night terrors?

Sudden arousal from SWS marked by intense fear and autonomic activation.

What is the relationship between sleep and memory?

SWS is associated with explicit memory consolidation, while REM sleep is linked to implicit memory.

What is the effect of lesions in the pons?

Lesions in this area abolish REM sleep and disrupt muscle atonia during REM episodes.

What is the typical duration of REM sleep in adults?

Adults spend about 2 hours in REM sleep during an 8-hour night.

What is somnambulism?

Sleepwalking that occurs during non-REM sleep (stage 3 SWS).

What are vertex spikes?

Negative EEG potentials that appear as a person becomes more drowsy.

What is the significance of high-frequency EEG activity in dreaming?

A greater ratio of high-frequency to low-frequency EEG activity in the posterior cortex predicts dreaming.

How does the hypothalamus relate to sleep regulation?

The hypothalamus contains orexin neurons that regulate wakefulness and sleep states.

What is learning?

The acquisition of new information.

What is memory?

The retention and later retrieval of learned information.

What is habituation?

A decrease in response to a repeatedly presented stimulus.

What is dishabituation?

An increase in response to a previously habituated stimulus upon presentation of a strong stimulus.

What is sensitization?

Prior strong stimulus facilitates responding.

What type of amnesia did patient H.M. suffer from?

Anterograde amnesia.

What brain areas were removed in patient H.M. to control his seizures?

Large portions of the anterior temporal lobes.

What is retrograde amnesia?

Inability to retrieve memories from a period prior to brain damage.

What is anterograde amnesia?

Inability to form new memories after the onset of brain damage/illness.

What type of memory is normal in patient H.M.?

Short-term memory (STM).

What type of memory is severely compromised in patient H.M.?

Long-term memory (LTM).

What task could H.M. learn despite his memory deficits?

A mirror-tracing task (procedural memory).

What is Korsakoff's syndrome?

A condition causing anterograde amnesia due to vitamin B1 deficiency, often related to alcoholism.

What type of amnesia does patient N.A. have?

Anterograde amnesia for verbal material.

What type of memory remains intact in patient K.C.?

General knowledge of facts.

What is the effect of emotional arousal on memory?

It affects memory consolidation.

What are place cells?

Hippocampal neurons that preferentially fire when the rat is in a particular spatial location.

What did Maguire et al. (2000) find about London cabdrivers?

They show larger posterior hippocampi compared to matched controls, with volume correlating positively with taxi driving experience.

What is the role of synaptic plasticity in memory?

Changes in synapses may be the mechanism of memory formation.

What changes occur in enriched environment (EC) rats?

Heavier cerebral cortices, enhanced cholinergic activity, and greater dendritic branching.

What is the significance of the serial position curve?

It shows primacy and recency effects in memory recall.

What brain regions are critical for encoding new declarative memories?

Medial temporal (hippocampal) and diencephalic structures.

What is the difference between short-term memory (STM) and long-term memory (LTM)?

Different cognitive and biological processes underlie STM and LTM.

What is the gill withdrawal response in Aplysia an example of?

Animal models of learning and memory.

What occurs during short-term habituation in the Aplysia gill withdrawal reflex?

Less neurotransmitter release and presynaptic Ca2+ influx with repeated stimulations.

What is long-term habituation in the Aplysia gill withdrawal reflex characterized by?

Retraction of sensory neuron synaptic terminals.

Who proposed the concept of Hebbian synapses?

Donald Hebb.

What does Hebb's dual trace hypothesis suggest?

Learning experiences create neural activity that helps build a stable change in the nervous system, forming a long-lasting memory trace.

What is long-term potentiation (LTP)?

A stable and enduring enhancement in synaptic transmission.