Motor planning brings human primary somatosensory cortex into action-specific preparatory states

Motor planning plays a critical role in producing fast and accurate movement. Yet, the neural processes that occur in human primary motor and somatosensory cortex during planning, and how they relate to those during movement execution, remain poorly understood. Here we used 7T functional magnetic resonance imaging (fMRI) and a delayed movement paradigm to study single finger movement planning and execution. The inclusion of no-go trials and variable delays allowed us to separate what are typically overlapping planning and execution brain responses. Although our univariate results show widespread deactivation during finger planning, multivariate pattern analysis revealed finger-specific activity patterns in contralateral primary somatosensory cortex (S1), which predicted the planned finger action. Surprisingly, these activity patterns were as informative as those found in contralateral primary motor cortex (M1). Control analyses ruled out the possibility that the detected information was an artifact of subthreshold movements during the preparatory delay. Furthermore, we observed that finger-specific activity patterns during planning were highly correlated to those during execution. These findings reveal that motor planning activates the specific S1 and M1 circuits that are engaged during the execution of a finger press, while activity in both regions is overall suppressed. We propose that preparatory states in S1 may improve movement control through changes in sensory processing or via direct influence of spinal motor neurons.

Four Artists: Angels and Mentors

Interwoven into my life at the loom are the stories of four women: a weaver, a painter, an embroiderer, and a fiber artist. Their histories have guided and pulled me forward in my own growth as an artist. Yet it is to their art that I feel a heartfelt, visceral, and almost spiritual resonance. I would like to present to the TSA conference in 2020 my research into the lives of Sumiko Deguchi (1883-1952), Helen Frankenthaler (1928- 2011), Adya van Rees-Dutilh (1876- 1959), and Pat Hickman (b.1935). As an artist who has wound, tied, dyed, and woven silk into contemporary ikat work for over forty years, I have become fascinated by how the thread reveals a life and encodes memory. There are many questions I would con- sider as I research the lives and work of these four women: • How does connection of fingertips on thread inform and guide the artist? • How does touch inform the somatosensory cortex in the brain? • How are the artist’s spirit and heart strings revealed in a viewer’s kines- thetic response to the luster and tactile presence of fiber? • What draws us to look closely at the intelligence within a textile or a canvas? Including images of the development of my own work, I hope to illustrate how their art has been an inspiration, a consolation, and an integral part of the fabric of my life’s work. Shouldering a vital textile tradition within a historic and vibrant contemporary community of fiber artists has been the thread I follow with my own voice.

Perceived Timing of Cutaneous Vibration and Intracortical Microstimulation of Human Somatosensory Cortex

BackgroundElectrically stimulating the somatosensory cortex can partially restore the sense of touch. Though this technique bypasses much of the neuroaxis, prior studies with non-human primates have found that conscious detection of touch elicited by intracortical microstimulation (ICMS) lags behind the detection of vibration applied to the skin. These findings may have been influenced by a mismatch in stimulus intensity; typically, vibration is perceived as more intense than ICMS, which can significantly impact temporal perception.ObjectiveThe goal of this study was to evaluate the relative latency at which intensity-matched vibration and ICMS are perceived in a human subject.MethodsA human participant implanted with microelectrode arrays in somatosensory cortex performed a reaction time task and a temporal order judgment (TOJ) task. In the reaction time task, the participant was presented with ICMS or vibration and verbal response times were obtained. In the TOJ task, the participant was sequentially presented with a pair of stimuli – ICMS followed by vibration or vice versa – and reported which stimulus occurred first.ResultsWhen ICMS and vibration were matched in perceived intensity, the reaction time to vibration was ∼50 ms faster than ICMS. However, in the TOJ task, ICMS and vibratory sensations arose at comparable latencies, with points of subjective simultaneity that were not significantly different from zero.ConclusionsBecause the perception of ICMS is slower than that of intensity-matched vibration, it may be necessary to stimulate at stronger ICMS intensities (thus decreasing reaction time) when incorporating ICMS sensory feedback into neural prostheses.

Sensory cortical dynamics during optical microstimulation training

Primary sensory cortex is a key locus of plasticity during learning. Exposure to novel stimuli often alters cortical activity, but isolating cortex-specific dynamics is challenging due to extensive pre-cortical processing. Here, we employ optical microstimulation of pyramidal neurons in layer (L) 2/3 of mouse primary vibrissal somatosensory cortex (vS1) to study cortical dynamics as mice learn to discriminate microstimulation intensity. Tracking activity over weeks using two-photon calcium imaging, we observe a rapid sparsification of the photoresponsive population, with the most responsive neurons exhibiting the largest declines in responsiveness. Following sparsification, the photoresponsive population attains a stable rate of neuronal turnover. At the same time, the photoresponsive population increasingly overlaps with populations encoding whisker movement and touch. Finally, we find that mice with larger declines in responsiveness learn the task more slowly than mice with smaller declines. Our results reveal that microstimulation-evoked cortical activity undergoes extensive reorganization during task learning and that the dynamics of this reorganization impact perception.

Morphological Changes in the Somatosensory Cortex of Guinea Pigs Following Simulation of the Abdominal Surgery Wound

The aim of research was to study the effect of the abdominal wall injuries and ascorbic acid (AA) on morphometric parameters of the somatosensory cortex.Material and methods. The density of the arrangement of neurons, sizes of nuclei and perikaryons of neurons, density and area of blood vessels in the somatosensory cortex were detected in guinea pigs after simulation of the abdominal wall injury. The process was accompanied by the parenteral administration of AA.Results. Simulation of the abdominal wall injury in guinea pigs resulted in a decreased thickness of the somatosensory cortex and a decreased density of neurons arrangement (on average by 32-37%). In 7 days after the operation, the exposed animals demonstrated a decreased density of blood vessels by 14–18%, the size of blood vessels also decreased by 27–46%; the fact evidencing a deterioration in the blood supply to the somatosensory cortex in the postoperative period. The effect of AA was mainly manifested in the increased size of the nuclei and perikaryons of neurons (by 20–40%); this evidencing activation of their metabolic activity. The most significant changes in the studied parameters were observed in the outer granular and, to a lesser extent, in the pyramidal and inner granular cytoarchitectonic layers.Conclusion. Experimental abdominal surgical interventions resulted in a decreased size and density of blood vessels in the somatosensory cortex. The results obtained can be used to develop methods of postoperative rehabilitation with the inclusion of drugs that improve blood supply and metabolism of the brain neurons. AA potentiates some of the effects of surgery on the somatosensory cortex; currently, there are no sufficient data to recommend it as a neuroprotective agent in the postoperative period.

The orexin system: a potential player in the pathophysiology of absence epilepsy?

Background : Absence epilepsy is characterized by the presence of spike-and-wave discharges (SWDs) at the EEG generated within the cortico-thalamo-cortical circuit. The molecular mechanisms involved in the pathophysiology of absence epilepsy are only partially known. WAG/Rij rats older than 2-3 months develop spontaneous SWDs, and they are sensitive to anti-absence medications. Hence, WAG/Rij rats are extensively used as a model for absence epilepsy with predictive validity. Objective : To examine the possibility that the orexin system, which supports the wake status in experimental animals and humans, plays a role in the pathophysiology of absence seizures. Methods : The perspective grounds its method on recent literature along with measurements of orexin receptor type-1 (OX1) protein levels in the thalamus and somatosensory cortex of WAG/Rij rats and non-epileptic Wistar control rats at two ages (25 days and 6-7 months). OX1 protein levels were measured by immunoblotting. Results : The analysis of the current literature suggests that the orexin system might be involved in the pathophysiology of absence epilepsy and might be targeted by therapeutic intervention. Experimental data are in line with this hypothesis showing that OX1 protein levels were reduced in the thalamus and somatosensory cortex of symptomatic WAG/Rij rats (6-7 months of age) with respect to non-epileptic controls, whereas these differences were not seen in pre-symptomatic, 25 days-old WAG/Rij rats. Conclusions : This might pave the way to future studies on the involvement of the orexinergic system in the pathophysiology of SWDs associated with absence epilepsy and its comorbidities.

Effects of stimulus pulse rate on somatosensory adaptation in the human cortex

BackgroundIntracortical microstimulation (ICMS) of the somatosensory cortex can restore sensation to people with neurological diseases. However, many aspects of ICMS are poorly understood, including the effect of continuous stimulation on percept intensity over time.ObjectiveHere, we evaluate how tactile percepts, evoked by ICMS in the somatosensory cortex of a human participant adapt over time.MethodsWe delivered continuous and intermittent ICMS to the somatosensory cortex and assessed the reported intensity of tactile percepts over time in a human participant. Experiments were conducted across approximately one year and linear mixed effects models were used to assess significance.ResultsContinuous stimulation at high frequencies led to rapid decreases in intensity, while low frequency stimulation maintained percept intensity for longer periods. Burst-modulated stimulation extended the time before the intensity began to decrease, but all protocols ultimately resulted in complete sensation loss within one minute. Intermittent stimulation paradigms with several seconds between stimulus trains also led to decreases in intensity on many electrodes, but never resulted in extinction of sensation after over three minutes of stimulation. Additionally, longer breaks between each pulse train resulted in some recovery of the stimulus-evoked percepts. For several electrodes, intermittent stimulation had almost no effect on the perceived intensity.ConclusionsIntermittent ICMS paradigms were more effective at maintaining percepts, and given that transient activity in the somatosensory cortex dominates the response to object contact, this stimulation method may mimic natural cortical activity and improve the perception of stimulation over time.

Heparin-Binding Growth-Associated Molecule (Pleiotrophin) Affects Sensory Signaling and Selected Motor Functions in Mouse Model of Anatomically Incomplete Cervical Spinal Cord Injury

Heparin-binding growth-associated molecule (pleiotrophin) is a neurite outgrowth-promoting secretory protein that lines developing fiber tracts in juvenile CNS (central nervous system). Previously, we have shown that heparin-binding growth-associated molecule (HB-GAM) reverses the CSPG (chondroitin sulfate proteoglycan) inhibition on neurite outgrowth in the culture medium of primary CNS neurons and enhances axon growth through the injured spinal cord in mice demonstrated by two-photon imaging. In this study, we have started studies on the possible role of HB-GAM in enhancing functional recovery after incomplete spinal cord injury (SCI) using cervical lateral hemisection and hemicontusion mouse models. In vivo imaging of blood-oxygen-level-dependent (BOLD) signals associated with functional activity in the somatosensory cortex was used to assess the sensory functions during vibrotactile hind paw stimulation. The signal displays an exaggerated response in animals with lateral hemisection that recovers to the level seen in the sham-operated mice by injection of HB-GAM to the trauma site. The effect of HB-GAM treatment on sensory-motor functions was assessed by performance in demanding behavioral tests requiring integration of afferent and efferent signaling with central coordination. Administration of HB-GAM either by direct injection into the trauma site or by intrathecal injection improves the climbing abilities in animals with cervical hemisection and in addition enhances the grip strength in animals with lateral hemicontusion without affecting the spontaneous locomotor activity. Recovery of sensory signaling in the sensorimotor cortex by HB-GAM to the level of sham-operated mice may contribute to the improvement of skilled locomotion requiring integration of spatiotemporal signals in the somatosensory cortex.