Biology subjects

Gigg, J.

Publications and source records attributed to Gigg, J..

3 recordsLinked to original sources

bioRxiv2020

Dissociating the effects of distraction and proactive interference on object memory through tests of novelty preference

Encoding information into memory is sensitive to distraction whilst retrieving that memory may be compromised by proactive interference from pre-existing memories. These two debilitating effects are common in neuropsychiatric conditions but modelling them preclinically to date is slow as it requires prolonged operant training. A step change would be the validation of functionally equivalent but fast, simple, high-throughput tasks based on spontaneous behaviour. Here, we show that spontaneous object preference testing meets these requirements in the subchronic phencyclidine (scPCP) rat model for cognitive impairments associated with schizophrenia. scPCP rats show clear memory sensitivity to distraction in the standard novel object recognition task (stNOR). However, due to this, stNOR cannot assess proactive interference. Therefore, we compared scPCP performance in stNOR to that using the continuous NOR task (conNOR), which offers minimal distraction, allowing disease-relevant memory deficits to be assessed directly. We first determined that scPCP treatment did not affect whisker movements during object exploration. scPCP rats exhibited the expected distraction stNOR effect but had intact performance on the first conNOR trial, effectively dissociating distraction by using two NOR task variants. In remaining conNOR trials, scPCP rats performed above chance throughout but, importantly, their detection of object novelty was increasingly impaired relative to controls. We attribute this effect to the accumulation of proactive interference. This is the first demonstration that increased sensitivity to distraction and proactive interference, both key cognitive impairments in schizophrenia, can be dissociated in the scPCP rat using two variants of the same fast, simple, spontaneous object memory paradigm.

animal behavior and cognition↗

bioRxiv2020

Local and global dichotomic dysfunction in resting and evoked functional connectivity precedes tauopathy

Functional network activity alterations are one of the earliest hallmarks of Alzheimers disease (AD), detected prior to amyloidosis and tauopathy. Better understanding the neuronal underpinnings of such network alterations could offer mechanistic insight into AD progression. Here, we examined a mouse model (early-tauopathy 3xTgAD mice) recapitulating this early AD stage. We found resting functional connectivity loss within ventral networks, including the entorhinal cortex, aligning with the spatial distribution of tauopathy reported in humans. Unexpectedly, in contrast to decreased connectivity at rest, 3xTgAD mice show enhanced fMRI signal within several projection areas following optogenetic activation of the entorhinal cortex. We corroborate this finding by demonstrating neuronal facilitation within ventral networks and synaptic hyperexcitability in projection targets. 3xTgAD mice thus reveal a dichotomic hypo-connected resting/hyper-responsive active phenotype. The strong homotopy between the areas affected supports the translatability of this pathophysiological model to tau-related deficits in humans.

neuroscience↗

bioRxiv2018

A new test of value-modulated attentional bias in mice

The allocation of attention can be modulated by the emotional value of a stimulus. In order to understand the biasing influence of emotion on attention allocation further, we require an animal test of how motivational salience modulates attention. In mice, female odour triggers arousal and elicits emotional responses in males. Here, we determined the extent to which objects labelled with female odour modulated the attention of C57BL/6J male mice. Seven experiments were conducted, using a modified version of the spontaneous Novel Object Recognition task. Attention was operationalised as differential exploration time of identical objects that were labelled with either female mouse odour (O+), a non-social odour, almond odour (Oa) or not labelled with any odour (O-). In some experiments we tested trial unique (novel) objects than never carried an odour (X-). We found that when single objects were presented, as well as when two objects were presented simultaneously (so competed with each other for attention), O+ received preferential attention compared to O-. This result was independent of whether O+ was at a novel or familiar location. When compared with Oa at a novel location, O+ at a familiar location attracted more attention. Compared to X-, O+ received more exploration only when placed at a novel location, but attention to O+ and X- was equivalent when they were placed in a familiar location. These results suggest that C57BL/6J male mice weigh up aspects of odour, object novelty and special novelty for motivational salience, and that, in some instances, female odour elicits more attention (object exploration) compared to other olfactory stimuli and visual object novelty. The findings of this study pave the way to using motivationally-significant odours to modulate the cognitive processes that give rise to novel object recognition.

neuroscience↗