speech & sleep

7/31/2019 Speech & Sleep

1/6

,

Hem ispheric spec ialization,

speec h and sleep

Dr Richard Vic ke ry

Room 308D Wallac e Wurth Building

Richard .Vick [email protected] u9385 1676

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nSensory and motor functions

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nMany functions show hemispheric specialization

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How does the brain integrate the hemispheres?n

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The two halves of the brain

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This operation is still performed, withthe latter third of the CC spared,e

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2/6

Hemispheric control of speechn

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Right hemisphereBilateralLeft hemisphereHandednesseci

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Language centres lie between

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The specialised language areas inter-connect

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Signals related to spoken words pass from auditory cortex toWernickes area (2).

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input from Wernickes area via the arcuate fasciculus (3).

Damage to small regions of cortex causesse ec ve anguage pro ems ca e ap as as

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from Bear et al., Neuroscience: exploring the brain


3/6

Combining written and spoken language

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The electroencephalogram is an extracellular-

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from Bear et al., Neuroscience: exploring the brain

Large EEG signals are due to synchronised cellr ng e n s pe ma se zure

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from epilepsygroup.com/education.html

What is sleep?

Sleep: a reversible behavioral state ofpercep ua sengagemen rom anunresponsiveness to the environment.

There are three physiological behavioural states

of arousal in man & other mammals and birds:WakeNon-REM sleeple

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REM sleep

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the asleep brain is the activity going on in the

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unaffected.


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Polygraphic Monitoring of sleep states

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Wake EEG - Desynchronized-

Non-REM sleep EEG - Synchronized(esp. stages 3-4) EMG - Attenuated but present

REM sleep EEG - DesynchronizedEMG - Absent (active paralysis)

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State: awake and relaxed

EOG

EOG

EEG

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EEG

SEMG

ECG

>50% of each epoch contains alpha activity (box)

Relatively high submental (under-chin) EMG tone

State: non-REM stage 4 (deep sleep)

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>50 of the epoch will have Delta EEG activity The EOG leads will mirror all of the Delta EEG Activit Submental EMG activity will be slightly reduced from

that of light sleep


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State: REM sleep

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Rapid eye movements

Mixed fre uenc EEG

Low tonic submental EMG

Control of sleep

The reticular formation plays a key role in the sleep / wakecycle. Ascending projections change the state of the

a amus o a ow sensory ransm ss on w en awa e an nREM sleep, while suppressing it in non-REM sleep. Spinal cord

ro ections cause aral sis durin REM slee . The reticularformation has centres that use neuromodulators such asnoradrenaline, serotonin and ACh to have diffuse effects.

The reticular formation is in turn driven by centres such as thesuprachiasmic nucleus of the hypothalamus that set thele

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crca an r y m. e suprac asm c nuceus ge s npu romphotoreceptive ganglion cells that use melanopsin, anddrives s nchronization of the slee wake c cle to ni ht da .

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There are faster rhythm such as the ~90 minute ultradianrh thm which is enerated in the medulla. Alertnesssleepiness alternate on an ultradian cycle, superimposed onthe slower circadian cycle.

The balance of modulatory neurotransmitters

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locus coeruleus:

noradrenaline

raphe:

serotonin

basal forebrain & pons:

acet lcholine

cortex:

GABA

wake high high high (forebra in) low

REM sleep low low high (forebra in & pons) low

non-REM sleep low low low high

Alternation and consolidation

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EC - entorhinal cortex; DG, CA3 and CA1 are parts of the hippocampus.

Consolidation appears to depend on alternation between REMand non-REM sleep deep sleep stages produce short-lived states

.

Power, 2004, PNAS 101: 1795


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Staging of sleep through the night

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Total Sleep Requirement

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Proportion of REM sleep decreases throughout,

helps the brain integrate new experiences

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Physiology

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Objectives:

Explain the meaning of hemisphericspec a za on an em sp er c om nance.

Describe the ori in and s m toms of Broca's,Wernicke's and conduction aphasias.

.

Describe the differences in brain states betweenwakefulness, non-REM sleep and REM sleep.

speech & sleep

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