6 - Rhythms in the Brain Flashcards
What is a rhythm?
A cyclical process repeats over time
How do you describe rhythmic patterns?
Shape of the waveform
Amplitude (strength)
Frequency (how often pattern repeats)
Phase (lag)
What type of brain rhythms are active during waking and sleeping?
- High frequency, low amplitude indicate waking and alterness, and dreaming
- Low frequency, high amplitude indicate non-dreaming sleep
What is the rhythm that is active during wakeful relaxation?
Alpha (~8Hz), suppressed when eyes are open
What is the synchrony hypothesis?
Neurons responding to the same object synchronise
E.g. firing in motion, ITC (object, category) and V4 (colour) will all fire in one pattern to a dog and another to a woman
What promotes binding in brain rhythms?
Attention
Strong gamma-band coherance
What kind of things do rhythmic core functions regulate?
Breathing, heart rate, oxygen and C02 levels
What regulates and monitors carbon dioxide and oxygen?
Medulla oblongata
Dynamically changes HR and respiration to changing conditions
What are the different categories of biorhythms?
Cicannual ~365 days
Infradian >24 hours
Circadian ~24 hours
Ultradian <24 hours
What does the SCN regulate?
Circadian rhythms.
Lesions abolish free-running rhythms.
Describe the circadian rhythm in humans
Runs around 24.2-25 hours.
The SCN runs on a single-cell basis (20,000) with each cell having it’s own clock.
The sun resets the clock daily.
How is the biological clock reset by the sun?
Intrinsically reset by photosensitive retinal ganglion cells which project to the SCN
