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Attention (Maintenance of Attention (Nobre (2004) (Pre cue, array of…

- - - - valid vs invalid cues
      - endogenous: arrow, exogenous: peripheral cue
      - respond to stimulus that appears on left or right of central fixation cross following a cue
    - - neutral or peripheral cue before delay and stimulus
      - 2 stimuli of varying orientations, asked to indicate which had higher contrast
      - attention increased apparent contrast, allowing better discrimination
  - - - stream monitoring task, ERPs
      - ERPs to identical stimuli greater for attended than non attended
    - - dissociable modulations of P1, N1 to valid and invalid trials of Posner
    - - V1, V2, V4 in 2 monkeys
      - 2 slowly drifting achromatic gratings presented for several seconds, attention within or outside receptive field
      - rewarded for releasing bar in change of colour to attended stimulus
      - neuronal responses to IN greater than OUT
      - backward progression: V4 greatest, V1 least
  - - - cells in monkey V4/IT trained to attend to stimuli in one location and ignore others
      - following training, the attended stimulus response was restored and unattended reduced (as if no stimulus present)
    - - Attention increases gain of direction selective neurons in M1 without narrowing direction turning curves
      - random dot displays inside receptive field vs outside were about 10% larger
  - - - Single unit activity and field potentials (summation of postsynaptic response across populations)
      - synchrony between spikes and ongoing gamma activity in V4 during attention or ignoring the location of stimuli
      - showed increased high frequency gamma and increased synchrony between spikes during attention
  - - - orientation change detection task which cued for 80% chance correct
      - showed that attention improved performance and decreased V4 firing rates
      - due to decrease covariance between neurons (80%) and reduced variance of single neurons
- - - - DISENGAGES attention from current locus
    - - SHIFTS attention to relevant location
    - - FILTERS irrelevant information
  - - - trained monkeys to make responses to the dimming of a peripheral target while ignoring a flashing distractor.
      - after characterising the RF of FEF neurons, stimulated FEF neuron below threshold and measured V4 actiivity
      - systematic changes in V4 activity for neurons with compatible RF, which correlated with enhanced discriminability of targets
    - - TMS to stimulate FEF in humans during an orienting task requiring participants to discriminate the direction of an arrow
      - LRP activity in motor cortex
      - When TMS applied to right FEF at the same time as stimulus presentation, performance disrupted on incongruent and enhanced on congruent
    - - injected muscimol to inactivate FEF neurons in macaques
      - produced profound and spatially specific deficits in memory guided saccades and increased latency/scatter/duration of visually guided
      - although v4 activity actually increased, stimulus discriminability of V4 responses during fixation and presaccadic period was impaired
      - increased influence of non RF stimuli on V4 activity and less about the target itself.
    - - recorded responses of single FEF neurons in monkeys trained to remember cued locations in order to detect changes in targets embedded among distractors in a task that did not involve saccades.
      - FEF neurons persistently encoded cued location through delay and discrimination
      - FEF activity reliably predicted whether monkeys could detect the target change
      - peripheral cue (target location), 2 flashes of target and had to indicate if stimulus changed orientation
    - - fMRI in shifting attention, shifting eye movement vs fixation
      - frontal and parietal regions were active, including the FEF to eye movement and covert attention task, large degree of overlap between shifting and eye movement.
  - - - Event related fMRI
      - Black background with white outline boxes and fixation cross, cue was overlapping yellow and blue arrows and told which to attend to (overtly)
      - superior frontal, inferior parietal and superior temporal cortex active to cues
      - After ISI, target checkerboards bilaterally, answer if cued stimulus contained grey or just black/white checks, ignoring uncured stimuli
      - cue was overlapping yellow and blue arrows, told which to attend to (covertly orient attention to the area indicated by the arrow)
    - - FEF: oculomotor control
      - IPS: spatial reference frames
      - PFC: maintaining task sets
    - - TPJ, VFC
    - - recorded simultaneously from LIP, FEF & dlPFC during endogenous and exogenous search tasks.
        
        Exogenous showed parietal before frontal
        
        Endogenous showed frontal before parietal
    - - PET scanning in covert attention task, whereby peripheral cues indicated the location of the subsequent targets
        
        medial and lateral premotor cortex
        
        anterior cingulate gyrus
        
        IPS in posterior parietal cortex
- - - - attend to different locations and measured tonic firing rate
      - increased overall spiking activity from baseline in cells for attended stimuli
    - - fixation on a central point while complex colourful images presented in periphery sequentially or simultaneously
      - cued by prior stimulus, compared activity in attended vs unattended
      - greater activity in extra striate, parietal and frontal in anticipation of the stimulus
  - - - alpha band oscillatory activity during the cue-stimulus interval of an endogenous spatial cuing paradigm
      - cued spatial locations were in upper or lower VF, Ts or moving dots
      - sustained increases in alpha band activity to the ignored location and desynchronisation to the to-be-attended stimulus
    - - Information is gated by inhibiting task irrelevant regions and routing information to task relevant regions
      - this is done by ossicilatory activity in alpha band
        
        reflects pulsed inhibition every 100ms
    - - phase of EEG alpha rhythm in posterior brain regions predicts both subsequent detection and stimulus elicited cortical activity
      - when a visual target presentation coincides with the trough of an alpha wave, cortical activation is suppressed as early as 100ms after stimulus alpha power