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The functional organisation and role in visually guided behaviour of the top-down projection from anterior cingulate cortex to primary visual cortex

Broom, Eluned 2019. The functional organisation and role in visually guided behaviour of the top-down projection from anterior cingulate cortex to primary visual cortex. PhD Thesis, Cardiff University.
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The interplay between bottom-up and top-down projections help the brain to build a perception of the visual world. Top-down projections, in particular, are believed to influence perception using previous experience and current context. One way in which they do this is in the direction of visual attention. Anterior cingulate cortex (ACC), a structure from which top-down projections are believed to emanate from, has been implicated in tasks requiring visual attention. Furthermore, studies in mice have shown an attentional-like effect in primary visual cortex (V1) neurons when a projection originating from ACC and terminating at V1 was artificially stimulated using optogenetics. The aim of the following studies was to determine whether ACC influenced the direction of visual attention under endogenous conditions. To do this, two main approaches were taken. First, the functional organisation of ACC axons in V1 were compared to layer 2/3 V1 pyramidal neurons in order to investigate whether the two populations were retinotopically matched. Secondly, the activity of ACC axons during a visually guided discrimination task was examined to discern whether it was elevated when mice performed well. This was achieved using calcium sensitive genetic indicators including gCaMP6s and jrGECO1a to record neuronal activity while awake, behaving, head-restrained mice completed visual tasks. To investigate functional organisation, a retinotopic protocol was run where mice passively viewed gratings in 36 separate locations. The visual discrimination task consisted of a reward-based go/no-go structure. It was found that significantly fewer ACC axons exhibited spatially specific responses than layer 2/3 V1 neurons. As well as this, instead of retinotopically matching layer 2/3 V1 neurons, ACC axons lying superficially to them relayed information about a wider ii area of visual space in both azimuth and elevation. Although some ACC axons showed orientation selectivity, grouping them by the orientation preference did not result in any retinotopic matching. Together, these results demonstrated that ACC axons do not appear to be as visually responsive as or retinotopically matched to layer 2/3 V1 somas in the same location in V1 under passive conditions. As well as this, it was found that ACC activity was not greater when mice performed trials correctly compared to incorrectly in visually guided tasks. This elevated activity appeared to occur during the response phase of the task and, in particular, in trials where mice carried out the motor response of licking. Taken together, these data suggested the neural projection from ACC to V1 was not involved directly in the perception of the visual stimulus, even when its onset could be predicted, and was instead associated with the motor response of the animal. On top of this, the activity of a fraction of these ACC axons appeared to be modulated by the addition of a reward. Overall, the data presented here indicates that the ACC projection to V1 is involved in visually guided tasks but is associated more with the motor response of licking than the perception of the visual stimulus. The additional modulation by reward suggests that this association depends upon the outcome of trials and may therefore be important for behaviours such as reward timing.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Biosciences
Date of First Compliant Deposit: 4 October 2019
Last Modified: 23 Jul 2020 02:14

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