Biology subjects

Bollimunta, A.

Publications and source records attributed to Bollimunta, A..

4 recordsLinked to original sources

bioRxiv2020

Head-mounted microendoscopic calcium imaging in dorsal premotor cortex of behaving rhesus macaque

A major effort is now underway across the brain sciences to identify, characterize and manipulate mesoscale neural circuits in order to elucidate the mechanisms underlying sensory perception, cognition and behavior. Optical imaging technologies, in conjunction with genetically encoded sensors and actuators, serve as important tools toward these goals, allowing access to large-scale genetically defined neuronal populations. In particular, one-photon miniature microscopes, coupled with genetically encoded calcium indicators and microendoscopic gradient-refractive index (GRIN) lenses, enable unprecedented readout of neural circuit dynamics in cortical and deep subcortical brain regions during active behavior in rodents. This has already led to breakthrough discoveries across a wide array of rodent brain regions and behaviors. However, in order to study the neural circuit mechanisms underlying more complex and clinically relevant human behaviors and cognitive functions, it is crucial to translate this technology to non-human primates. Here, we describe the first successful application of this technology in the rhesus macaque. We identified a viral strategy for robust expression of GCaMP, optimized a surgical protocol for microendoscope GRIN lens insertion, and created a chronic cranial chamber and lens mounting system for imaging in gyral cortex. Using these methods, we demonstrate the ability to perform plug-and-play, head-mounted recordings of cellular-resolution calcium dynamics from over 100 genetically-targeted neurons simultaneously in dorsal premotor cortex while the macaque performs a naturalistic motor reach task with the head unrestrained and freely moving. The recorded population of neurons exhibited calcium dynamics selective to the direction of reach, which we show can be used to decode the animals trial-by-trial motor behavior. Recordings were stable over several months, allowing us to longitudinally track large populations of individual neurons and monitor their relationship to motor behavior over time. Finally, we demonstrate the ability to conduct simultaneous, multi-site imaging in bilateral dorsal premotor cortices, offering an opportunity to study distributed networks underlying complex behavior and cognition. Together, this work establishes head-mounted microendoscopic calcium imaging in macaque as a powerful new approach for studying the neural circuit mechanisms underlying complex and clinically relevant behaviors, and promises to greatly advance our understanding of human brain function, as well as its dysfunction in neurological disease. HighlightsFirst demonstration of head-mounted microendoscopic calcium imaging in behaving macaque. Surgical protocols developed for preparing the animal for calcium imaging, including virus injections to express GCaMP and chronic implantation of a GRIN lens to enable optical access to gyral cortex. Proof of concept plug-and-play calcium imaging in behaving macaques with months long stable recording capability allowing populations of individual neurons to be tracked longitudinally. Bilateral calcium imaging from dorsal premotor cortex exhibited dynamics selective to the animals direction of reach and allowed decoding of the animals motor behavior

neuroscience↗

bioRxiv2019

Midbrain activity supports high-level visual properties in primate temporal cortex

The evolution of the primate brain is marked by a dramatic increase in the number of neocortical areas that process visual information 1. This cortical expansion supports two hallmarks of high-level primate vision - the ability to selectively attend to particular visual features 2 and the ability to recognize a seemingly limitless number of complex visual objects 3. Given their prominent roles in high-level vision for primates, it is commonly assumed that these cortical processes supersede the earlier versions of these functions accomplished by the evolutionarily older brain structures that lie beneath the cortex. Contrary to this view, here we show that the superior colliculus (SC), a midbrain structure conserved across all vertebrates 4, is necessary for the normal expression of attention-related modulation and object selectivity in a newly identified region of macaque temporal cortex. Using a combination of psychophysics, causal perturbations and fMRI, we identified a localized region in the temporal cortex that is functionally dependent on the SC. Targeted electrophysiological recordings in this cortical region revealed neurons with strong attention-related modulation that was markedly reduced during attention deficits caused by SC inactivation. Many of these neurons also exhibited selectivity for particular visual objects, and this selectivity was also reduced during SC inactivation. Thus, the SC exerts a causal influence on high-level visual processing in cortex at a surprisingly late stage where attention and object selectivity converge, perhaps determined by the elemental forms of perceptual processing the SC has supported since before there was a neocortex.

neuroscience↗

bioRxiv2018

Focal disruption of temporal cortex in macaque during midbrain-induced neglect

Spatial neglect is a common clinical syndrome involving disruption of the brains attention-related circuitry, including the dorsocaudal temporal cortex. While neglect is readily modeled in macaques, the absence of evidence for temporal cortex involvement has suggested a fundamental difference from humans. To map the neurological expression of spatial neglect in macaques, we measured attention-related fMRI activity across the cerebral cortex during experimental induction of neglect through reversible inactivation of the superior colliculus. During inactivation, monkeys exhibited hallmark attentional deficits of neglect in tasks using either moving or static stimuli. The behavioral deficits were accompanied by marked reductions in fMRI attentional modulation that were strongest in a small region on the floor of the superior temporal sulcus. Notably, direct inactivation of this mid-STS cortical region caused similar neglect-like spatial attention deficits. These results identify a putative macaque homolog to temporal cortex structures known to play a central role in human neglect.\n\nHighlightsO_LIDuring neglect the mid-STS cortex shows largest reduction in attentional modulation\nC_LIO_LIThe mid-STS cortex is selectively affected with static as well as dynamic stimuli\nC_LIO_LIMid-STS cortex is affected during neglect caused by SC or FEF inactivation\nC_LIO_LIInactivation of mid-STS cortex itself causes neglect without eye movement deficits\nC_LI\n\nIn BriefUsing fMRI in macaques performing attention tasks combined with reversible inactivations, Bogadhi et al. provide causal evidence that a region on the floor of the superior temporal sulcus is a crucial node in the cortical control of covert selective attention and a putative homolog to temporal cortex regions in humans implicated in spatial neglect.

neuroscience↗

bioRxiv2018

Brain regions modulated during covert visual attention in the macaque

Neurophysiology studies of covert visual attention in monkeys have emphasized the modulation of sensory neural responses in the visual cortex. At the same time, electrophysiological correlates of attention have been reported in other cortical and subcortical structures, and recent fMRI studies have identified regions across the brain modulated by attention. Here we used fMRI in two monkeys performing covert attention tasks to reproduce and extend these findings in order to help establish a more complete list of brain structures involved in the control of attention. As expected from previous studies, we found attention-related modulation in frontal, parietal and visual cortical areas as well as the superior colliculus and pulvinar. We also found significant attention-related modulation in cortical regions not traditionally linked to attention - mid-STS areas (anterior FST and parts of IPa, PGa, TPO), as well as the caudate nucleus. A control experiment using a second-order orientation stimulus showed that the observed modulation in a subset of these mid-STS areas did not depend on visual motion. These results identify the mid-STS areas (anterior FST and parts of IPa, PGa, TPO) and caudate nucleus as potentially important brain regions in the control of covert visual attention in monkeys.

animal behavior and cognition↗