Final Flashcards

Question

Heterogeneous Layering

Answer 1

* Blob (V1) – Region in the visual cortex that contains color-sensitive neurons – Revealed by staining for cytochrome oxidase * Interblob (V1) – Region that separates blobs – Participates in the perception of form and motion

Answer 2

* Each retinal ganglion cell (RGC) responds to stimulation on just a small circular patch of the retina—the cell’s receptive field. * Coding location – Light falling on one place on the retina will activate one ganglion cell, and light falling on another place will activate a different ganglion cell.

Answer 3

* Cells in the lateral geniculate nucleus (LGN) also have visual fields. * Each LGN cell represents a particular place. * Projects to V1, forming a topographic map – Receptive fields of cells in the cortex are typically larger than those of retinal ganglion cells. – More cortical tissue is devoted to cells in the fovea than in the periphery.

Answer 4

- The receptive fields of many retinal ganglion cells .... - combine to form the receptive field of a single lateral geniculate nucleus (LGN) cell ... - the receptive fields of many LGN cells combine to form the receptive field of a single V1 cell

Answer 5

* The corpus callosum connects the two hemispheres but only specific brain structures. – Most of the frontal lobes are connected. – The occipital lobes have almost no connections * Exception: Cells that lie along the midline of the visual field are connected so that their receptive fields overlap.

Answer 6

– Respond only to the presence or absence of light, not to shape (job of the cortex) – Concentric circle arrangement * Center and surround (periphery) * Luminance contrast - The amount of light reflected by an object relative to its surroundings - This allows input from RGCs to tell the brain about shape.

Answer 7

* Neighbouring retinal ganglion cells receive their inputs from an overlapping set of photoreceptors. – Receptive fields overlap. * A small spot of light shining on the retina is likely to produce activity in both on-center and off-center ganglion cells.

Answer 8

* V1 neurons receive input from multiple RGCs. * V1 neurons have a much larger receptive field than RGCs. * Cells behave like orientation detectors. – Excited by bars of light oriented in particular directions * Simple cells – Receptive field with a rectangular on-off arrangement * Complex cells – Are maximally excited by bars of light moving in a particular direction through the receptive field. * Hypercomplex cells – Are like complex cells, maximally responsive to moving bars. – Have strong inhibitory area at one end of the receptive field.

Answer 9

* Sensory inputs enter the cortical column at layer VI (bottom) and terminate on stellate cells in layer IV that synapse with pyramidal cells in layers III and V. * The information flow is vertical. * Axons of the pyramidal cells leave the column to join other columns or structures.

Answer 10

▪Represent a very small portion (2-3 %) of ganglion cells in the mammalian retina ▪In response to light, ipRGCs are capable of depolarizing without any synaptic input from other photoreceptors (intrinsically photosensitive) * M1-M5 subtypes * Differences in morphology and projections * Circadian brain areas predominantly innervated by M1 subtype * Brn3 family of transcription factors regulates the differentiation of RGCs

Answer 11

* Anticipate rhythmic changes in the environment – Anticipate vs. respond to event * Temporal organization of behaviour – Avoid predators and competitors * Biological rhythms – Daily or seasonal changes in physiology and behaviour – Related to: * Earth’s rotation about its axis * Earth’s progression around the sun

Answer 12

* Our biology is most closely tied to daily variations, rather than seasonal cycles * Dominated by rhythm of daytime activity and nighttime sleep – We don’t migrate, we’re not seasonal breeders * Rhythms in more than activity/rest – Pulse, blood pressure, body temperature, cell division, blood cell count, alertness, metabolic rate, sexual drive, response to medication, hormone levels ... Examples of human rhythms: * Physiological parameters – Hormones * Cortisol, melatonin – Body temperature * Psychological parameters – Alertness – Reaction time

Answer 13

* Wide variety of biological rhythm * Infradian – more than daily – Estrus or menstrual cycles * Ultradian – less than daily – BRAC (basic-rest activity cycle) – Respiration – Eating

Answer 14

* Usually use a running wheel connected to computer * Can use other measures too – Perch hopping – Physiological measures Rhythms in time-free environments * Test humans in bunkers or caves * Note that period is >24h – 1h later each day * “Freerunning” rhythm

Answer 15

* A clock isn’t much good if it doesn’t predict something – Don’t just generate rhythms – Also need to synchronize to the environmental cycles * Even though our circadian clock runs a little slow, we exhibit 24h patterns in behavior and physiology * Like a cheap watch, our clock needs to be reset each day.

Answer 16

* Permits it to track changing dawn / dusk – Unless you live near the equator, day length can change quite a bit over the year

Answer 17

* Sunrise / sunset * Socialinteraction * Exercise * Food * Each of these gives information about time – Zeitgeber (German for time-giver) * Zeitgebers synchronize the circadian clock through entrainment

Answer 18

* Light is the most potent zeitgeber – Most obvious cue as to if it is day or night – Can synchronize and reset the circadian clock * Light in the early morning or late evening is the best cue – Nudges the clock ahead or back respectively * The deeper light falls into the night, the bigger the effect – Maximal around body temperature minimum

Answer 19

* Edison’s Curse: – The light bulb has allowed people to be active at times of the day when we normally wouldn’t be – Shift workers working at times when the body would normally be sleeping – Rotating shift workers constantly jumping to new shifts * Increase rates – On the job accidents – Disease

Answer 20

- When SCN is removed, mice become completely arrhythmic, they have “broken clocks”, no temporal organization - Important experiment to determine function of SCN: tau mutant hamsters with fast clocks, lesioned SCN, complete arythmancy as a result, then took SCN from animal with regular clock (24 hour) and implanted into tau hamster, restored rhythm and now the period followed the donor’s clock (regular 24 hour), showed that SCN sets rhythm - SCN looked at outside of animal, each cell is ticking on its own, SCN cells are rhythmic on their own - SCN at the base of hypothalamus, main clock that sets the rhythm of other body cloths

Answer 21

* Transcription- translation feedback loop – A gene is activated – mRNA is produced – protein being produced cytoplasm – The protein feeds back into the nucleus and turns off its own transcription

Answer 22

* There are three “period” genes (Period 1, 2, 3) * Mutations in period 2 and 3 have been associated with human sleep disorders – Advance sleep phase syndrome (Period 2) – Delayed sleep phase syndrome (Period 3) * Similar to the hamster Tau mutation * Hamster has a mutant enzyme (casein kinase 1 epsilon), humans have a mutant site on the period gene where the same enzyme acts

Answer 23

* The SCN may not drive behaviours directly * SCN lesioned animals still eat, drink and sleep, they just do it haphazardly – The SCN is controlled by light – The SCN controls rhythms target neural structures – These targets regulate the behaviour * May be an oscillator for each

Answer 24

* We break our 24 hour day into bouts of wake and sleep – Spend about 1/3rd of our lives asleep * “Wake” is a complex state that includes a wide variety of behaviours – Eating, drinking, thinking, exercising, sex * “Sleep” is often thought of as “not wake” * Sleep is also a complex state with many distinct parts – Resting, napping, deep sleep, snoring, dreaming, sleepwalking

Answer 25

* Sleep trends are highly variable and change throughout life. * Typically sleep quality and quantity decreases as you age. * Average adult should get between 7-8 hours of sleep – Some get much less or much more

Answer 26

1) EEG: electroencephalograph – Cortical electrical activity – Primary measure of sleep – Described in terms of frequency and amplitude of waves 2) EMG: Electromyograph – Muscle tone 3) EOG: Electrooculograph – Eye movements

Answer 27

* Wake: – Small amplitutde, high frequency EEG (15-30Hz) – EEG pattern: Beta * Relaxed wakefulness, eyes closed – Alpha – Amplitude a little higher, frequency a little lower * (7-11 Hz) – Sign that the membrane potentials of cortical neurons are becoming more synchronized

Answer 28

* There are 2 main divisions of sleep * Slow Wave sleep (SWS) (Non-REM sleep, N-sleep) – EEG activity has increasing amplitude and decreasing frequency – 3 stages: progressive changes in EEG * Paradoxical Sleep (REM sleep, R-Sleep) – Wake-like EEG

Answer 29

* All Non-REM sleep is characterized by: – Some muscle tone/activity – Slow rolling eye movements – Drop in body temperature, heart rate, breathing * Progresses from low amplitude / high frequency to high amplitude / low frequency

Answer 30

* Transition from wake into sleep * Lasts several minutes * low amplitude, mixed frequency – Includes 4-7Hz Theta Waves * Muscles have tone and eyes can be rolling

Answer 31

* EEG gets a little slower and higher amplitude * Also shows: – Sleep spindles (11-16Hz) – K Complexes (Very high amplitude)

Answer 32

* Slow wave sleep or deep sleep (in humans) * High amplitude low frequency (0.5-2Hz) – Delta waves * Muscle tone

Answer 33

* Low amplitude, high frequency * Resembles wake EEG with beta waves – Called paradoxical sleep * Rapid eye movements (REMs) * Dreams!!! * Muscle atonia – Antigravity muscles shut off – Some muscle movements: eye muscles, muscles in the middle ear, diaphragm * Some twitching in postural muscles

Answer 34

* 1st half of night predominated by slow wave sleep – Little REM * Last half predominated by REM – Little or no Stage 3 or 4 * Drift between slow wave and REM in about a 90-minute cycle

Answer 35

* Slow wave sleep – Little dreaming – Lack of content, more like vague images – Night terrors * REM – Rich dreams, occur in real time – Nightmares – More frequent and longer dreams as night progresses – Memory function is impaired, so dreams are difficult to remember the next day * Actually, anything that occurs during sleep is hard to remember

Answer 36

1) Biological adaptation (energy conservation) * Inactivity * Low brain activity during NREM * Body temperature drops * But... don’t save that much more than you would just resting, where vigilance would be higher – Also, what about REM? 2) Sleep as a restorative process – At the end of the day, you feel tired – After a nights sleep you feel refreshed – Irritable, decreased attention after not enough sleep – World record of no sleep is about 11 days – Little effect on person – SWS made up first, followed by a rebound in REM * Total sleep loss: – Rats will die in about 4 weeks without sleep – Metabolism gets totally messed up – Rest helps physical fatigue – Sleep necessary to relieve mental fatigue 3) Memory storage – Theory: Sleep facilitates the storage of memories - Best theory!! - During REM, circuits become activated that were active during training - Birds learning a new song will show activation in auditory areas during REM sleep - Sleep deprivation decreases performance on learned tasks

Answer 37

* NREM sleep seems to be most important for explicit/declarative memories – Word learning in humans – Spatial learning in rodents * REM sleep seems to be most important for implicit, non-declarative memories

Answer 38

* Acetylcholine from the brainstem Reticular Activating System and basal forebrain are important for wake * RAS stimulation leads to wake-like EEG * RAS lesion = persistent coma

Answer 39

Raphe(serotonin) and Locus coeruleus (Norepinephrine) * All project widely in cortex * All are active during wake * Silent during REM sleep – Antidepressants suppress REM – Antidepressants promote 5-HT and NE

Answer 40

* Found in the dorsolateral hypothalamus * Project to many of the wake centers – Activates them * Projects to the cortex too, promotes arousal * These cells die in narcolepsy – The sleep/wake and REM system become deregulated.

Answer 41

* Learning: permanent change in behaviour as a result of experience * Memory: ability to recall or recognize previous experience – A product of a physical trace or engram – Two categories: Implicit memory (unconscious) and explicit memory (conscious) * Can also be discussed in terms of procedural memory and declarative memory

Answer 42

Short term memory: stores sensory, motor, and cognitive memory Long term memory: divided into explicit (CONSCIOUS personal, autobiograohical, facts) implicit (UNCONCSIOUS skills, habits, priming), and emotional memory (attraction, fear...)

Answer 43

* Encoding is the process by which information is stored in the brain – Implicit memories: data-driven or bottom-up processing – Explicit memories: conceptually driven or top-down processing * All memory is fallible! * Learning and memory is not localized to one brain region!

Answer 44

Pavlovian conditioning – Learning procedure whereby a neutral stimulus such as a tone (CS) comes to elicit a response (CR) because of its repeated pairing with some event such as the delivery of food (UCS) Operant Conditioning – Learning procedure in which the consequences (such as obtaining a reward) of a particular behaviour (such as pressing a bar) increase or decrease the probability of the behavior occurring again (Edward Thorndike, 1898) – Thorndike's Puzzle Box: A cat gradually learned that its actions had consequences (The cat touched the releasing mechanism by chance on the initial trials as it paced inside box, cat learned that something it did opened the door, and it tended to repeat its behaviours from just before the door opened)

Answer 45

* Medial temporal region -entorhinal cortex -parahippocampal cortex -perirhinal cortex * Prefrontal cortex

Answer 46

* William Scoville performed a bilateral medial temporal lobe resection on a young man, Henry Molaison (H. M.). – Seizures originated in the region of the amygdala, hippocampal formation, and associated subcortical structures, so Scoville removed them bilaterally. * After the surgery, H. M. had severe amnesia, lacking explicit memory. – He could not recall anything that happened after the surgery. * H. M.’s performance on implicit memory tests was left intact.

Answer 47

* Patient J. K. – Impaired implicit memory with intact explicit memory * Developed Parkinson disease in his mid-70s and started to have memory problems at 78 – Damage to basal ganglia * Impaired ability to perform tasks that he had done all his life – Example: turning off the radio * Could still recall explicit events

Answer 48

Mishkin et al. 1987, 1997, proposed: 1. The neocortex receives sensory and motor info 2. The basal ganglia receives inputs from the neocortex and substantia nigra 3. The basal ganglia projects to the ventral thalamus 4. Ventral thalamus projects to premotor cortex

Answer 49

- Primate study: trained them to displace objects to get food, recognition phase with certain objects involving memory, lesioned the hippocampus and then they were unable to do this - Study on drivers in London: larger parts of the hippocampus in those with better navigational abilities

Answer 50

Code spatial information * Place cells: fire when organism is in a spatial location, regardless of orientation * Grid cells: fire at many locations, forming a virtual grid of the environment

Answer 51

* Versatility at the synaptic level provides a mechanism for learning – a relatively permanent change in behaviour that results from experience. “Cells that fire together, wire together!” Two general types of behaviour have been studied in Aplysia: * Habituation: learning behaviour in which a response to a stimulus weakens with repeated presentations. * Sensitization: learning behaviour in which a response to a stimulus strengthens with repeated presentations, because the stimulus is novel or stronger than normal.

Answer 52

* Long term potentiation (LTP): Long-lasting increase in synaptic effectiveness after high- frequency stimulation (e.g., 100 Hz) - Long lasting permanent increase in synaptic effectiveness, example of neuroplasticity 1) Weak electrical stimulation: because the NDMA receptor is blocked by a magnesium ion, release of glutamate by a weak electrical stimulation activates only the AMPA receptor 2) Strong electrical stimulation (depolarizing EPSP): a strong electrical stimulation can depolarize the postsynaptic membrane sufficiently that the magnesium ion is removed from the NMDA receptor pore 3) Weak electrical stimulation: now glutamate, released by weak stimulation, can activate the NMDA receptor to allow CA2+ influx, which through a second messenger, increases the function or number of AMPA receptors or both

Answer 53

Long term depression (LTD): Long- lasting decrease in synaptic effectiveness after low-frequency stimulation (e.g., 5 Hz)

Answer 54

May influence how memory circuits are strengthened. Some individuals may naturally have higher neuroplasticity, allowing for more efficient memory formation.