Lecture 20: NS VI - Integrative Brain

How does sleep occur?

in cycles

circadian rhythm

physical, mental and behavioral changes that follow a 24-hour cycle; biological clock

what is sleep?

a temporary state of unconsciousness from which one can awaken when stimulated

characteristic of sleep

1. stereotyped posture (lying down, eyes closed)
2. sleep paralysis (inhibition of muscular activity)

How does sleep have a restorative effect?

1. replenish energy sources such as glycogen and ATP
2. REM sleep consolidates and strengthens memories by reinforcing some synapses and eliminating others (in hippocampus of cerebral cortex)
3. increase in growth hormone secretion

T or F: sleep deprivation isn't fatal to experimental animals

F; sleep deprivation can be fatal to experimental animals

what does EEG stand for?

electroencephalogram

what does an EEG represent?

fluctuations in brain electrical activity in voltage as a waveform of variable frequency and amplitude

why are EEGs important?

they help in diagnosis of degenerative diseases (e.g. epilepsy), metabolic abnormalities, and brain tumors

brain waves

rhythmic voltage changes resulting from synchronized local potentials, not action potentials in the superficial layers of the cerebral cortex

frequency

number of waves per second

amplitude

size of a wave

what is a common occurrance in brain death?

lack of brain waves

types of EEG waves

1. alpha
2. beta
3. theta
4. delta

types of EEG waves - alpha

awake but resting (eyes closed)

types of EEG waves - beta

eyes open and performing mental tasks

types of EEG waves - theta

drowsy or sleepy in adults; common in awake children

types of EEG waves - delta

deep sleep (adults)

what two different general phases can sleep be divided into?

1. REM (Rapid eye movement sleep)
2. NREM (non-REM) sleep

What are the three stages of non-REM (NREM) sleep?

N1 (stage 1 sleep)
N2 (stage 2 sleep)
N3 (stage 3 and 4 sleep)

sleep stages - characteristics of relaxed wakefulness

early portion of stage 1 sleep produces alpha waves; the person is very relaxed but still awake; these waves are high frequency low amplitude

sleep stages - characteristics of N1

As an individual continues through stage 1 sleep, there is an increase in theta wave activity

how much time do we spend in N1 sleep?

1-7 minutes (5% of sleep time)

sleep stages - characteristics of N2

stage 2; state of deep relaxation; theta waves dominate brain activity, but they are interrupted by sleep spindles and K-complexes

how much time do we spend in N2 sleep?

45% of sleep time

what are sleep spindles and K complexes? when do they occur?

brief bursts of activity during N2 (stage 2) sleep

sleep stages - characteristics of N3

stage 3 and 4 sleep; AKA "deep sleep or slow-wave sleep"; heart rate and respiration slow dramatically; consolidation of memories and sleep walking occur during this stage; waves are low frequency high amplitude

how much time do we spend in N3 sleep?

25%

Example question: slow-wave sleep (stage N3) is a sleep stage characterized by:
1. light/deep sleep
2. dreaming/not dreaming
3. low/high muscle tone

1. deep sleep
2. not dreaming
3. high muscle tone

where does dreaming occur?

REM sleep; we have vivid and long dreams but muscle paralysis during this stage prevents us from acting out dreams

what does REM stand for?

rapid eye movement; eyes move back and forth during this stage of sleep

what is REM sleep also known as? why?

dreaming sleep or "paradoxical sleep"; it is called paradoxical sleep because there is high brain activity but a lack of muscle tone/movement

what is REM atonia?

motor neurons are not being stimulated; muscles are paralyzed during REM sleep (except circulation and respiratory muscles)

what does the EEG of REM sleep look like?

it resembles the waking state; increased vital signs (temperature, heart rate, respiration, blood pressure)

T or F: Penile/clitoral erection and pupil constriction during N3 sleep

false; penile/clitoral erection and pupil constriction occurs during REM sleep

what is structure is known as the "body's master biological clock"?

suprachiasmatic nucleus (SCN)

how does the suprachiasmatic nucleus (SCN) receive information?

via the retinohypothalamic tract

what hormone is secreted during the dark phase of the circadian rhythm? what is it secreted by?

melatonin is secreted by the pituitary gland

where is the pituitary gland located?

below the hypothalamus

what hormone is secreted during the light phase of the circadian rhythm? what is it secreted by?

orexin is secreted by the lateral hypothalamus

what does melatonin do?

triggers the onset of sleep; regulates circadian rhythm and energy balance

what does orexin do?

regulates wakefulness and food intake

what does input from the eyes allow the SCN to do?

allows SCN to synchronize multiple body rhythms (clocks) with external rhythms of night and day

examples of body functions regulated by circadian rhythms

sleep, body temp, urine production, hormone secretion/cortisol levels, etc.

hypnogram

illustration of how an individual moves through the various stages of sleep in a night

how do sleep stages change throughout the night?

REM sleep increases as the night progresses and time in other stages decreases; we have more dreams at the end of the night

how many times do we repeat the sleep cycle during the night?

4-5 times

what do emotional feeling result from?

interaction between the prefrontal cortex (PFC) and the diencephalon

what categorizes emotional experiences as either pleasant or unpleasant?

limbic system

prefrontal cortex role in emotion

seat of judgement, intent, control over the expression of emotions (how we show feelings to others)

striatum role in emotion

may be involved in avoidance of stimuli paired with aversive events and habit formation

amygdala role in emotion

receives input from sensory systems and sends that info to cortical structures; plays a role in fear, food intake, sexual behavior, and stress responses; also sends output to different brain areas

hypothalamus role in emotion

influences somatic and visceral motor systems (increase HR and BP, hair standing on end, vomiting)

hippocampus role in emotion

memory consolidation of emotional events

cognition

range of mental processes by which we acquire and use knowledge

examples of cognition

sensory perception, thought, reasoning, judgement, memory, imagination, intuition

3 functional areas of the cerebral cortex

1. primary sensory areas
2. primary motor areas
3. association areas

3 functional areas of cerebral cortex - primary sensory areas

receive somatic sensory impulses including:
-the 5 special senses (olfaction/smell, gustation/taste, equilibrium/balance and body position, vision, and hearing)
-general senses: cutaneous sensations and some proprioception (sense of self-movement, body position)
-little visceral sensory information is routed to the cortex

3 functional areas of cerebral cortex - primary motor areas

these areas generate impulses that move through descending motor tracts to innervate voluntary skeletal muscles

3 functional areas of cerebral cortex - association areas

this is where cognition (integration of info) occurs; we have both association sensory areas and association motor areas in the cortex that are located very close to one another

what does the parietal lobe do?

helps perceive and attend to stimuli; controls fine sensation (detects detail and judges texture, size, weight, and shape)

contralateral neglect syndrome

cognitive defect in parietal lobe; unaware of objects or their own limbs on opposite side of the body

example of contralateral neglect syndrome

a person cannot detect details of half of a picture they are copying so they only draw half of it

what does the frontal lobe do?

helps us think about the world and plan/execute appropriate behavior (involved in social interaction and problem solving)

what do prefrontal cortex lesions cause?

personality disorders and socially inappropriate behaviors

what does the temporal lobe do?

helps identify stimuli

agnosia

a lesion in the temporal lobe causes inability to recognize and identify familiar objects

prosopagnosia

a lesion in the temporal lobe causes inability to recognize faces or facial expression

a patient cannot identify her car keys. This person probably has a lesion in certain association areas of the _________ lobe.
A) frontal
B) parietal
C) temporal
D) occipital

C) temporal: this is an example of agnosia

what do primary sensory areas do?

receive sensory impulses

what do association sensory areas do?

integrate incoming sensory information

example of primary sensory and association sensory areas

primary auditory cortex: receives auditory signals in the temporal lobe
auditory association area: this area in the temporal lobe aids in understanding spoken words

where is the primary motor cortex located?

precentral gyrus of the frontal lobe

where is the primary somatosensory cortex located?

in the postcentral gyrus of the parietal lobe

what is the function of the primary somatosensory cortex?

provides awareness of stimulus; these regions of the cerebral cortex are related to the general (somatosensory, somesthetic, or somatic) senses; distributed over entire body

what does the somatosensory association area do?

makes cognitive sense of stimulus

sensory homunculus

diagram of the sensory inputs to the primary somatosensory cortex

motor homunculus

map of primary motor cortex showing control of skeletal muscles

what is the amount of cerebral tissue devoted to a given body region proportional to on a sensory homunculus?

the amount of cerebral tissue given to a body region on the sensory homunculus diagram is proportional to how richly innervated and sensitive that region is

what is the motor area devoted to a specific body region proportional to on a motor homunculus?

it is proportional to the number of motor units involved in the region's control

sensory info from the ____________ nerves is transmitted to the cerebral cortex by the _________________ tracts (somatosensory pathways)

peripheral; ascending

the ___________ processes the input from ascending tracts and selectively relays signals to the _______________ gyrus

thalamus; postcentral

what cells are located in upper motor neurons?

pyramidal cells

what are the 3 phases of voluntary movement control?

1. planning movement
2. initiating movement
3. executing movement

what happens during the planning movement stage of voluntary movement control?

the motor association area of the frontal lobe makes a plan for movement/muscle contraction by taking information from the basal nuclei and the cerebellum

what happens during the initiating movement stage of voluntary movement control?

the plan for movement is sent to the the primary motor cortex located in the precentral gyrus of the frontal lobe

what happens during the executing movement stage of voluntary movement control?

information from the primary motor cortex is sent via the corticospinal tract to the alpha motor neurons in the spinal cord to execute the movement

what brain structures correct errors in ongoing movements? how?

cerebellum and basal ganglia; the motor cortex sends information to both and these structures send information back via the thalamus

the output of the cerebellum is (in terms of regulating movement) ___________

excitatory (stimulates movement)

the output of the basal ganglia (in terms of regulating movement) is _____________

inhibitory; stops movement

what abilities does language include?

reading, writing, speaking, and understanding words

angular gyrus (parietal lobe)

important in the ability to read and write

left hemisphere vs. right hemisphere: Wernicke's area

left hemisphere: where Wernicke's area is physically located
right hemisphere: recognizes the emotional content of another person's speech; a lesion could make someone unable to understand a joke

left hemisphere vs. right hemisphere: Broca's area

left hemisphere: where Broca's area is physically located
right hemisphere: affective language area; a lesion would cause aprosody (flat, emotionless speech)

the _______________ aspect of language is controlled by regions in the opposite hemisphere that mirror these areas

emotional

aphasia

caused by lesions in Broca's or Wernicke's area; loss of ability to understand or express speech

fluent aphasia

AKA wernicke's aphasia; speech can be produced but the individual is unable to comprehend what other people are saying to them

nonfluent aphasia

AKA Broca's aphasia; the indivdiual can comprehend what others are saying to them but they can't produce fluent speech

cerebral hemispheres differ in _____________ and ___________

structure and function

T or F: One brain hemisphere can be dominant over the other

F; neither hemisphere is dominant, but each is specialized for certain tasks