Brain-machine interface learning is facilitated by specific patterning of distributed cortical feedback.

Neuroprosthetics offer great hope for motor-impaired patients. One obstacle is that fine motor control requires near-instantaneous, rich somatosensory feedback. Such distributed feedback may be recreated in a brain-machine interface using distributed artificial stimulation across the cortical surface.

Continuity within the somatosensory cortical map facilitates learning.

The topographic organization is a prominent feature of sensory cortices, but its functional role remains controversial. Particularly, it is not well determined how integration of activity within a cortical area depends on its topography during sensory-guided behavior. Here, we train mice expressing channelrhodopsin in excitatory neurons to track a photostimulation bar that rotated smoothly over the topographic whisker representation of the primary somatosensory cortex.

Mechanical coupling through the skin affects whisker movements and tactile information encoding.

Rats use their whiskers to extract sensory information from their environment. While exploring, they analyze peripheral stimuli distributed over several whiskers. Previous studies have reported cross-whisker integration of information at several levels of the neuronal pathways from whisker follicles to the somatosensory cortex.

A fast intracortical brain-machine interface with patterned optogenetic feedback.

Objective: The development of brain-machine interfaces (BMIs) brings new prospects to patients with a loss of autonomy. By combining online recordings of brain activity with a decoding algorithm, patients can learn to control a robotic arm in order to perform simple actions. However, in contrast to the vast amounts of somatosensory information channeled by limbs to the brain, current BMIs are devoid of touch and force sensors.

Representation of tactile scenes in the rodent barrel cortex.

After half a century of research, the sensory features coded by neurons of the rodent barrel cortex remain poorly understood. Still, views of the sensory representation of whisker information are increasingly shifting from a labeled line representation of single-whisker deflections to a selectivity for specific elements of the complex statistics of the multi-whisker deflection patterns that take place during spontaneous rodent behavior - so called natural tactile scenes. Here we review the current knowledge regarding the coding of patterns of whisker stimuli by barrel cortex neurons, from responses to single-whisker deflections to the representation of complex tactile scenes.

Bilateral Discrimination of Tactile Patterns without Whisking in Freely Running Rats.

A majority of whisker discrimination tasks in rodents are performed on head-fixed animals to facilitate tracking or control of the sensory inputs. However, head fixation critically restrains the behavior and thus the incoming stimuli compared with those occurring in natural conditions. In this study, we investigated whether freely behaving rats can discriminate fine tactile patterns while running, in particular when stimuli are presented simultaneously on both sides of the snout.

Bidirectional control of a one-dimensional robotic actuator by operant conditioning of a single unit in rat motor cortex.

The design of efficient neuroprosthetic devices has become a major challenge for the long-term goal of restoring autonomy to motor-impaired patients. One approach for brain control of actuators consists in decoding the activity pattern obtained by simultaneously recording large neuronal ensembles in order to predict in real-time the subject's intention, and move the prosthesis accordingly. An alternative way is to assign the output of one or a few neurons by operant conditioning to control the prosthesis with rules defined by the experimenter, and rely on the functional adaptation of these neurons during learning to reach the desired behavioral outcome.

"Master" neurons induced by operant conditioning in rat motor cortex during a brain-machine interface task.

Operant control of a prosthesis by neuronal cortical activity is one of the successful strategies for implementing brain-machine interfaces (BMI), by which the subject learns to exert a volitional control of goal-directed movements. However, it remains unknown if the induced brain circuit reorganization affects preferentially the conditioned neurons whose activity controlled the BMI actuator during training. Here, multiple extracellular single-units were recorded simultaneously in the motor cortex of head-fixed behaving rats.

Coding of apparent motion in the thalamic nucleus of the rat vibrissal somatosensory system.

While exploring objects, rats make multiple contacts using their whiskers, thereby generating complex patterns of sensory information. The cerebral structures that process this information in the somatosensory system show discrete patterns of anatomically distinct units, each corresponding to one whisker. Moreover, the feedforward and feedback connections are remarkably topographic, with little cross-whisker divergence before reaching the cortical network.

Disruption of ripple-associated hippocampal activity during rest impairs spatial learning in the rat.

The hippocampus plays a key role in the acquisition of new memories for places and events. Evidence suggests that the consolidation of these memories is enhanced during sleep. At the neuronal level, reactivation of awake experience in the hippocampus during sharp-wave ripple events, characteristic of slow-wave sleep, has been proposed as a neural mechanism for sleep-dependent memory consolidation.

Emergent properties of tactile scenes selectively activate barrel cortex neurons.

Rats discriminate objects by scanning their surface with the facial vibrissae, producing spatiotemporally complex sequences of tactile contacts. The way in which the somatosensory cortex responds to these complex multivibrissal stimuli has not been explored. It is unclear yet whether contextual information from across the entire whisker pad influences cortical responses.

Spatial selectivity and theta phase precession in CA1 interneurons.

Traditionally, most of the information processing of neural networks is thought to be carried out by excitatory cells. Likewise, recent evidence for temporal coding comes from the study of the detailed firing patterns of excitatory neurons. In the CA1 region of the rat hippocampus, pyramidal cells discharge selectively when the animal is in specific locations in its environment, and exhibit a precise relationship with the ongoing rhythmic activity of the network (phase precession).

Spatiotemporal characteristics of neuronal sensory integration in the barrel cortex of the rat.

In primary sensory cortices, neuronal responses to a stimulus presented as part of a rapid sequence often differ from responses to an isolated stimulus. It has been reported that sequential stimulation of two whiskers produces facilitatory modulations of barrel cortex neuronal responses. These results are at odds with the well-known suppressive interaction that has been usually described.

Acetylcholine-dependent potentiation of temporal frequency representation in the barrel cortex does not depend on response magnitude during conditioning.

The response properties of neurons of the postero-medial barrel sub-field of the somatosensory cortex (the cortical structure receiving information from the mystacial vibrissae can be modified as a consequence of peripheral manipulations of the afferent activity. This plasticity depends on the integrity of the cortical cholinergic innervation, which originates at the nucleus basalis magnocellularis (NBM). The activity of the NBM is related to the behavioral state of the animal and the putative cholinergic neurons are activated by specific events, such as reward-related signals, during behavioral learning.