Cogs176-lec13 (week 4) - Thalamic control of sensory selection in divided attention PDF

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Week 4 of SS1 - 2020...

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Paper: Thalamic control of sensory selection in divided attention -

We can enhance response to a stimulus and get higher response to that stimulus than others, larger signal to noise ratio Can decrease the noise → increase the response OR keep the noise the same and increase response to the stimulus Items in the brain being responded to most strongly are essentially equivalent to those that are attended (no matter what kind of attention is) Temporal coherence: getting neurons both responding to the same stimulus → spiking activity more sync under attention than inattention Sync firing follows an oscillation (40Hz gamma, also 20-30 Hz beta)

Third mechanism: 2 different kinds of inputs brain nuclei - Task: selection of bias to get thalamic lateral geniculate neurons firing vs medial geniculate neurons firing in response to a stimulus Prefrontal cortex - An association cortex - get input from different brain areas - Special incense - develops late in life (18 y/o) - Powerfully affects cognitive function when there’s abnormality/damage - show unusual activity/anatomy in disorders (OCD, hypofrontal) - Output of PFC - to almost all areas of cortex - impacts areas of primary visual cortex and how those neurons can modulate their responses - to thalamus - both specific and nonspecific nuclei (thalamic reticular nucleus) - to neuromodulatory systems Thalamic cortical system - There are subregions of cortex - visual, auditory, somatosensory - In thalamus - relay nuclei - train station of the brain - for info to come in and go out another way - Specific nuclei vs nonspecific nuclei - Lateral geniculate nucleus - input from retina, outputting to primary visual cortex - Medial geniculate nucleus - input from cochlear (sound vibrations hitting the eardrums), outputting to primary auditory cortex - Ventral basal nucleus - input from trigeminal nucleus in rat responding to whisker, output to somatosensory cortex - Thalamic reticular nucleus - surrounding not the whole thalamus - within are inhibitory GABA neurons with extensive interconnections - a net reticulum - send inhibitory projects down to the specific nuclei (LGN, VBN and MGN) - outputs from spec nuclei bifurcates - excite the primary cortices →

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non-REM: these neurons’ connections to each other are highly sync in activity spindle in stage 2 - reflects sync excitatory input from the spec thalamic nuclei What sync those cells in firing = having a thalamic reticular nucleus → inhibit and release together in a spindle frequency pattern Waking state: the cortical EEG is desynchronized (EEG low amplitude and faster, periods are more irregular) REM and waking: Spiking activity of the thalamic particular neurons NOT sync, spec nuclei are more independent

Paper - sophisticated recording of activity in the brain actually happening - Karl Deisseroth - development of genetic techniques for new forms of visualizing activity in the brain and manipulating brain very spec ways - Task: create an attentional paradigm - mouse at one to attend to visual and one time to auditory stimulus - Every trial: mouse standing with nose in a little poke of a hole - while stimuli presented, while waiting for stimuli, one/two tpes of sound cued to let it know what they attend to - Blue noise: 11 KHz - add noise and filter for higher frequency - Brown and blue noise = Cues to tell mouse how to pay attention - While mouse waiting, 2 lights up above and either one can go off - If light goes off → mouse poke nose in hole where light still on - Auditory stimulus: a sweep (low to high AND high to low) → mouse detect and learn over time (if high to low → mouse choose nose poke on left, if low to high → nose poke on right) - Most of the time, both stimuli are produced (light flashes and low/high sweep happen as well) → some trials - only attend to the sound OR the light (and ignore the other stimulus) - brown/blue noise tells mouse which stimulus to attend to → visual vs auditory stimulus - Error: 20-30% animals getting it right - How big/loud to make the stimuli so the visual and auditory yield the same amount of error? - If increase light intensity → accuracy increases (70%) - Cross-modal: not only respond to the visual stimulus but ignore a coincident auditory stimulus → do worse - Taxing animal attentional processes - During a series of cross-modal trials: sometimes omitted the other stimulus randomly - Do as well as both stimuli are presented - Cross-modal: have to use the brown/blue noise → visual or auditory - if take out the distractors → animal successfully detect the character of the stimulus attended to → top down attentional process: distractors don’t much matter (bottom up: distractors result in worse performance)

Top down control of attention to one’s modality stimulus (vision vs auditory) - Top down: PFC quickly followed - controlling the way we pay attention - PFC disruption: - VGAT: protein produced in GABA neurons - mice with VGAT will express channelrhodopsin - ion channel that inserts itself into the membrane of these GABA neurons and light sensitive → deliver light at a particular frequency and cause that channel to open - Disruption through activation of inhibitory neurons - inactivate synaptically through IPSPs - Errors increase but only works in the anticipation period → during disruption of PFC output - If disrupt during presentation period: no increase deficit, response is flat, PFC disrupt increases errors for both stimuli → PFC important during anticipation phase and for setting up brain to respond to light input vs auditory input - priming the visual system/audtory system appropriately based on the cue - Disrupt the visual cortex during anticipation phase: no effect, but during presentation phase → increase errors - Effect of the pFC is not mediated through PFC to visual cortex projection - Non supported model - Inhibiting the lateral geniculate nucleus itself: deficit in anticipation and presentation phase - If don't allow the disrupt of the activity in the thalamic neuron during anticipation phase → animal subsequently not respond properly to presentation phase Thalamic reticular nucleus - PFC projected to this - PRFC is capable of inhibiting.activating neurons in the thalamic reticular nucleus projecting to the lateral geniculate → affect visual/auditory inputs to cortex - PFC can selectively activate neurons projected to either medial or lateral genicular - Record in the thalamic reticular nucleus itself: - Thalamic reticular neurons project to lateral geniculate nucleus → inhibit the activity of LGN neurons that themselves provide excitatory visual input to the primary visual cortex → firing less - Attend to audition: neurons are enhanced in firing → inhibiting the LGN more less transmission of visual information through the LGN to the V1 → how selection occurs: - Vision attended: reduce inhibition on LGN - Audition attended: increase inhibition on LGN -

During attention to auditory: higher activity → if take away PFC: difference goes away In a nutshell: PFC operates through the thalamus to impact stimulus selection...