Angular tuning is preferential sensory response to a directional stimulus and is observed in the whisker tactile system. In whisker hair follicles, there are at least three types of low threshold mechanoreceptors (LTMRs): rapidly adapting (RA), slowly adapting type 1 (SA1), and slowly adapting type 2 (SA2). These LTMRs display angular tuning but their properties remain incompletely studied. Here we used isolated rat whisker hair follicles and pressure-clamped single-fiber recordings to study angular tuning of these LTMRs. Angular tuning was determined with impulses elicited by ramp-and-hold deflection of whisker hair in 24 directions each at 15° for a total of 360°. We show that RA display impulses during ramp-up, both ramp-up and ramp-down, or ramp-down dynamic phases. Both SA1 and SA2 respond to angular stimuli with slowly adapting impulses in most angles. However, SA1 and SA2 show rapidly adapting responses in other angles. All the three types of LTMRs display strong angular tuning, and there is no sign...

Hyperactivation of cyclin-dependent kinase 5 (CDK5) by p25, contributes to neuroinflammation causing neurodegeneration in Parkinson’s disease (PD) and Alzheimer's diseases (AD). However, the mechanism by which CDK5 induces neuroinflammation in the PD brain is largely unexplored. Here, we show that CDK5 phosphorylates cytosolic phospholipase A2 (cPLA2) at Thr-268 and Ser-505 sites lead to its activation and generation of eicosanoid products. Mutational studies using site-directed mutagenesis and molecular simulations show that the architecture of the protein changes upon each single-point mutation. Interestingly, double-mutations also led to a severe decline in the activity of cPLA2 and disruption of its translocation to the plasma membrane. Further, the brain lysates of transgenic PD mouse models show hyperactivation of CDK5 resulting in enhanced phosphorylation of Thr-268 and Ser-505 of cPLA2 and its heightened activity confirming the findings observed in the cell culture model of PD. These phosphorylatio...

Visual accuracy is consistently shown to be modulated around the time of the action execution. The neural underpinning of this motor-induced modulation of visual perception is still unclear. Here, we investigate with EEG whether it is related to the readiness potential, an event-related potential linked to motor preparation. Across 18 human participants, the magnitude of visual modulation following a voluntary button press was found to correlate with the readiness potential amplitude measured during visual discrimination. Participants' amplitude of the readiness potential in a purely motor-task was also found to correlate with the extent of the motor-induced modulation of visual perception in the visuomotor task. These results provide strong evidence that perceptual changes close to action execution are associated with motor preparation processes and that this mechanism is independent of task contingencies. Further, our findings suggest that the readiness potential provides a fingerprint of individual visu...

Zebrafish retinal cone signals shift in spectral shape through larval, juvenile, and adult development as expression patterns of eight cone-opsin genes change. An algorithm extracting signal amplitudes for the component cone spectral types is developed and tested on two thyroxin receptor β2 (trβ2) gain-of-function lines crx:mYFP-2A-trβ2 and gnat2:mYFP-2A-trβ2 , allowing correlation between opsin signaling and opsin immunoreactivity in lines with different developmental timing and cell-type expression of this red-opsin-promoting transgene. Both adult transgenics became complete, or nearly complete, ‘red-cone dichromats’, with disproportionately large LWS1 opsin amplitudes as compared to controls, where LWS1 and LWS2 amplitudes were about equal, and significant signals from SWS1, SWS2, and Rh2 opsins were detected. But in transgenic larvae and juveniles of both lines it was LWS2 amplitudes that increased, with LWS1 cone signals rarely encountered. In gnat2:mYFP-2A-trβ2 embryos at 5 days post fertilization (d...

When looking around a visual scene, humans make saccadic eye movements to fixate objects of interest. While the extraocular muscles can execute saccades in any direction, not all saccade directions are equally likely: saccades in horizontal and vertical directions are most prevalent. Here, we asked if head orientation plays a role in determining saccade direction biases. Study participants (n = 14) viewed natural scenes and abstract fractals (radially symmetric patterns) through a virtual reality headset equipped with eye tracking. Participants’ heads were stabilized and tilted at -30°, 0°, or 30° while viewing the images, which could also be tilted by -30°, 0°, and 30° relative to the head. To determine if the biases in saccade direction changed with head tilt, we calculated polar histograms of saccade directions and cross-correlated pairs of histograms to find the angular displacement resulting in the maximum correlation. During free viewing of fractals, saccade biases largely followed the orientation of...

A significant proportion of the human neurotypical population exhibits some degree of sensory eye dominance (SED), referring to the brain’s preferential processing of one eye’s input versus another. The neural substrates underlying this functional imbalance are not well known. Here, we investigated the relationship between visual white matter tract properties and SED in the human neurotypical population. Observers’ performance on two commonly used dichoptic tasks were used to index SED, along with performance on a third task to address a functional implication of binocular imbalance: stereovision. We show that diffusivity metrics of the optic radiations well predict behavioural SED metrics. We found no relationship between SED and stereosensitivity. Our data suggest that SED is not simply reflected by grey matter structural and functional alterations, as often suggested, but relates, at least in part to the microstructural properties of thalamocortical white matter. Significance Statement Sensory eye do...

Direction selective neurons in macaque primary visual cortex are narrowly tuned for orientation, and are thus afflicted by the aperture problem. At the next stage of motion processing, in the middle temporal (MT) area, some cells appear to solve this problem, responding to the pattern motion direction of plaids. Models have been proposed to account for this computation, but they do not replicate the diversity of responses observed in MT. We recorded from 386 cells in area MT of two male macaques, while presenting a wide range of random-line stimuli and their compositions into noise plaids. As we broadened the range of stimuli used to probe the cells, yielding ever more challenging conditions for extracting pattern motion, the diversity of the responses observed increased, and the fraction of cells that faithfully encoded pattern motion direction shrank. However, we show here that a pattern motion signal is present at the population level. We identified four mechanisms, one never proposed before, that toget...

Motivation is a powerful driver of learning and memory. Functional MRI studies show that interactions between the dopaminergic midbrain (SN/VTA), hippocampus, and nucleus accumbens (NAc) are critical for motivated memory encoding. However, it is not known if these effects are transient and purely functional, or if individual differences in the structure of this circuit underlie motivated memory encoding. To quantify individual differences in structure, diffusion-weighted MRI and probabilistic tractography were used to quantify SN/VTA-striatum and SN/VTA-hippocampus pathways associated with motivated memory encoding in humans. Male and female participants completed a motivated source memory paradigm. During encoding, words were randomly assigned to one of three conditions: reward ($1.00), control ($0.00), or punishment (-$1.00). During retrieval, participants were asked to retrieve item and source information of the previously studied words and were rewarded or penalized according to their performance. Sour...

The hippocampus is crucial for retrieval of contextual memories. The activation of a subpopulation of neurons in the dorsal CA1 (dCA1) of the hippocampus is required for memory retrieval. Given that hippocampal neurons exhibit distinct patterns of response during memory retrieval, the activity patterns of individual neurons or ensembles may be critically involved in memory retrieval. However, this relation has been unclear. To investigate this question, we employed an in vivo microendoscope calcium imaging technique to optically record neuronal activity in the dCA1 of male and female mice. We observed that a portion of dCA1 neurons increased their responses to the learned context after contextual fear conditioning (FC), resulting in overall increase in response of neuronal population compared with simple context exposure. Such increased response was specific to the conditioned context as it disappeared in neutral context. The magnitude of increase in neuronal responses by FC was proportional to memory stre...