Biology subjects

Tan, K. M.

Publications and source records attributed to Tan, K. M..

4 recordsLinked to original sources

bioRxiv2022

A non-lemniscal thalamic interface connecting alerting sensory cues to internal states in mice

Alterations in internal states, such as elevated arousal level and increased anxiety or fear, triggered by alerting environmental cues are required for behavioral state transitions promoting survival. However, the specific brain region that plays an interfacing role between alerting stimuli and internal states remains to be identified. Here, we report that the medial sector of the auditory thalamus (ATm), which consists of a group of non-lemniscal thalamic nuclei, can fulfill this function. VGluT2-expressing ATm (ATmVGluT2+) neurons receive direct and strong inputs from both visual and auditory midbrain regions, and project to multiple downstream structures critically involved in brain state regulation. Their activity was correlated with, and indispensable for, both blue light- and sound-induced NREM sleep-to-Wake transition, and their arousing effects were mainly mediated by, but not limited to, the temporal association cortices. ATmVGluT2+ neuron activation in awake behaving mice induced pupil dilation and behavioral responses suggestive of anxiety. Blocking the neurotransmitter release of ATmVGluT2+ neurons receiving auditory inputs selectively abolished loud noise-triggered escape behavior but not locomotion. Thus, the ATm is an interface in mouse brain that can transform alerting environmental cues into internal arousal and emotional state alterations that promote survival.

neuroscience↗

bioRxiv2019

Posttraumatic Stress Disorder and the Social Brain: Affect-Related Disruption of the Default and Mirror Networks

BackgroundSocial impairments, specifically in mentalizing and emotion recognition, are common and debilitating symptoms of posttraumatic stress disorder (PTSD). Despite this, little is known about the neural underpinnings of these impairments, as there have been no published neuroimaging investigations of social inference in PTSD. MethodsTrauma-exposed veterans with and without PTSD (N = 20 each) performed the Why/How social inference task during functional magnetic resonance imaging (fMRI). The PTSD group had two fMRI sessions, between which they underwent affect labeling training. We probed the primary networks of the "social brain"--the default mode network (DMN) and mirror neuron system (MNS)--by examining neural activity evoked by mentalizing and action identification prompts, which were paired with emotional and non-emotional targets. ResultsHyperactivation to emotional stimuli differentiated PTSD patients from controls, correlated with symptom severity, and predicted training outcomes. Critically, these effects were generally non-significant for non-emotional stimuli. PTSD-related effects were widely distributed throughout DMN and MNS. Effects were strongest in regions associated with the dorsal attention, ventral attention, and frontoparietal control networks. Unexpectedly, effects were non-significant in core affect regions. ConclusionsThe array of social cognitive processes subserved by DMN and MNS may be inordinately selective for emotional stimuli in PTSD. This selectivity may be tightly linked with attentional processes, as effects were strongest in attention-related regions. Putatively, we propose an attentional account of social inference dysfunction in PTSD, in which affective attentional biases drive widespread affect-selectivity throughout the social brain. This account aligns with numerous findings of affect-biased attentional processing in PTSD.

neuroscience↗

bioRxiv2018

Transformation of Speech Sequences in Human Sensorimotor Circuits

After we listen to a series of words, we can silently replay them in our mind. Does this mental replay involve a re-activation of our original perceptual representations? We recorded electrocorticographic (ECoG) activity across the lateral cerebral cortex as people heard and then mentally rehearsed spoken sentences. For each region, we tested whether silent rehearsal of sentences involved reactivation of sentence-specific representations established during perception or transformation to a distinct representation. In sensorimotor and premotor cortex, we observed reliable and temporally precise responses to speech; these patterns transformed to distinct sentence-specific representations during mental rehearsal. In contrast, we observed slower and less reliable responses in prefrontal and temporoparietal cortex; these higher-order representations, which were sensitive to sentence semantics, were shared across perception and rehearsal. The mental rehearsal of natural speech involves the transformation of time-resolved speech representations in sensorimotor and premotor cortex, combined with diffuse reactivation of higher-order semantic representations.\n\nConflict of interestThe authors declare no competing financial interests.

neuroscience↗

bioRxiv2018

Propagation of information along the cortical hierarchy as a function of attention while reading and listening to stories

How does attention route information from sensory to high-order areas as a function of task, within the relatively fixed topology of the brain? In this study, participants were simultaneously presented with two unrelated stories - one spoken and one written - and asked to attend one while ignoring the other. We used fMRI and a novel inter-subject correlation analysis to track the spread of information along the processing hierarchy as a function of task. Processing the unattended spoken (written) information was confined to auditory (visual) cortices. In contrast, attending to the spoken (written) story enhanced the stimulus-selective responses in early sensory regions and allowed it to spread into higher-order areas. Surprisingly, we found that the story-specific spoken (written) responses for the attended story also reached the opposite secondary visual (auditory) regions. These results demonstrate how attention enhances the processing of attended input and allows it to propagate across brain areas.

neuroscience↗