4 research outputs found
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Focal optogenetic suppression in macaque area MT biases direction discrimination and decision confidence, but only transiently
Insights from causal manipulations of brain activity depend on targeting the spatial and temporal scales most relevant for behavior. Using a sensitive perceptual decision task in monkeys, we examined the effects of rapid, reversible inactivation on a spatial scale previously achieved only with electrical microstimulation. Inactivating groups of similarly tuned neurons in area MT produced systematic effects on choice and confidence. Behavioral effects were attenuated over the course of each session, suggesting compensatory adjustments in the downstream readout of MT over tens of minutes. Compensation also occurred on a sub-second time scale: behavior was largely unaffected when the visual stimulus (and concurrent suppression) lasted longer than 350 ms. These trends were similar for choice and confidence, consistent with the idea of a common mechanism underlying both measures. The findings demonstrate the utility of hyperpolarizing opsins for linking neural population activity at fine spatial and temporal scales to cognitive functions in primates
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Flexible routing of information for decision making
Behaving in a complex world requires flexible mapping between sensory inputs and motor outputs. One must be able to make decisions about what actions to take based on a wide variety of inputs. This presents a routing problem: brain areas involved in decision making must receive information encoded by different sensory neurons in different situations. In this thesis I investigate this routing problem using two variations of the random dot motion task which require flexible routing. In the first, a single random dot motion task appears in different locations on different trials. Recording from the lateral intraparietal area (LIP) revealed several neural features which varied with stimulus location. A second task made it possible to disentangle routing from other signals, by separating the time of routing from the onset of motion and decision making. In this second task, a visual cue indicated the location at which relevant motion would appear. After the cue was extinguished, two random dot motion patches appeared. An informative patch appeared at the cued location, and an uninformative patch appeared at another location. Comparison of these two tasks revealed three location dependent signals at motion onset: a visual signal related to surround suppression, a second suppressive signal that may set the amount of evidence required for decision making, and a 12-20 hertz oscillation in firing rate. This oscillation appears to be a signature of flexible information routing. It appears at motion onset when the motion stimulus varies in location unpredictably; it appears at cue onset when a spatial cue indicates the location information must be routed from; and it does not appear when stimulus location is fixed and flexible routing is not required. Future work on this project will eventually require tools which are not well developed for use in rhesus macaques. The final chapter describes two projects which attempt to address this problem, one through the use of optogenetics in monkeys and the other by adapting an established monkey behavioral task for use in mice
Glycine receptor α3 and α2 subunits mediate tonic and exogenous agonist-induced currents in forebrain
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Vocabulary acquisition in young children: the role of the story
Sharing storybooks with babies increases their future
achievements in literacy, especially in reading (Hall, 2001; Moore and Wade, 1997, 2003; Scarborough et al., 1991; Wade and Moore, 1998; Wells, 1985). This study, focusing on case studies of two 20-month-old children, attempts to identify the role the storybook plays in children’s vocabulary acquisition. Their mothers adopted a regime of daily reading of specific picture books over a six-week period, and recorded the children’s acquisition of new vocabulary, in order to explore what specific contribution these texts made to the children’s speech. The findings demonstrate that storybooks form one source of children’s newly-acquired vocabulary. Factors that might account for this were more difficult to determine through a study of this scale