Transient changes of electrical activity in the rat barrel cortex during conditioning

Style and spectral power: processing of abstract and representational art in artists and non-artists

We investigated cortical activity in response to abstract and representational paintings in artists and non-artists. Participants engaged in visual inspection of works of art and recalled them immediately afterwards through mental imagery. Meanwhile, we recorded their EEG, and calculated the power of their alpha band and theta band activity afterwards. In accordance with previous studies, theta band and alpha band power differed between artists and non-artists; these differences were found to depend, however, on the abstract or representational character of the paintings. Differences between abstract and representational art, and between inspection and imagery, occurred in alpha band power for non-artists only and in theta band power for artists. These results were taken to suggest that effects in artists reflect sustained focused attention and perceptual flexibility; in non-artists motivation and engagement with the task. The results were essentially whole-head, despite the local character of the measurement.

Rat psychomotor vigilance task with fast response times using a conditioned lick behavior

Investigations into the physiological mechanisms of sleep control require an animal psychomotor vigilance task (PVT) with fast response times (<300 ms). Rats provide a good PVT model since whisker stimulation produces a rapid and robust cortical evoked response, and animals can be trained to lick following stimulation. Our prior experiments used deprivation-based approaches to maximize motivation for operant conditioned responses. However, deprivation can influence physiological and neurobehavioral effects. In order to maintain motivation without water deprivation, we conditioned rats for immobilization and head restraint, then trained them to lick for a 10% sucrose solution in response to whisker stimulation. After approximately 8 training sessions, animals produced greater than 80% correct hits to the stimulus. Over the course of training, reaction times became faster and correct hits increased. Performance in the PVT was examined after 3, 6 and 12 h of sleep deprivation achieved by gentle handling. A significant decrease in percent correct hits occurred following 6 and 12 h of sleep deprivation and reaction times increased significantly following 12 h of sleep deprivation. While behaviorally the animals appeared to be awake, we observed significant increases in EEG delta power prior to misses. The rat PVT with fast response times allows investigation of sleep deprivation effects, time-on-task and pharmacological agents. Fast response times also allow closer parallel studies to ongoing human protocols.

A novel method for precisely timed stimulation of mouse whiskers in a freely moving preparation: application for delivery of the conditioned stimulus in trace eyeblink conditioning

The somatosensory whisker pathway has been a useful system for increasing our understanding of experience-induced plasticity. However, precisely timed whisker activation in the awake freely moving mouse has been very difficult. This manuscript describes a method for construction of a whisker stimulator that can be attached to a freely moving mouse. The stimulator was used to activate the whiskers in a time-sensitive forebrain-dependent task, trace eyeblink conditioning. After repeatedly pairing whisker stimulation with delivery of a mild periorbital shock following a stimulus-free trace interval, trace-conditioned mice were able to learn the association. This study demonstrates the potential for using the whisker stimulator in time-sensitive behavioral tasks, such as trace eyeblink conditioning, thus enhancing our ability to examine experience-induced neuronal plasticity in the somatosensory whisker pathway in awake behaving rodents.

Conditioned lick behavior and evoked responses using whisker twitches in head restrained rats

To examine whisker barrel evoked response potentials in chronically implanted rats during behavioral learning with very fast response times, rats must be calm while immobilized with their head restrained. We quantified their behaviors during training with an ethogram and measured each individual animals' progress over the training period. Once calm under restraint, rats were conditioned to differentiate between a reward and control whisker twitch, then provide a lick response when presented with the correct stimulus, rewarded by a drop of water. Rats produced the correct licking response (after reward whisker twitch), and learned not to lick after a control whisker was twitched. By implementing a high-density 64-channel electrocorticogram (ECoG) electrode array, we mapped the barrel field of the somatosensory cortex with high spatial and temporal resolution during conditioned lick behaviors. In agreement with previous reports, we observe a larger evoked response after training, probably related to mechanisms of cortical plasticity.

Experience-dependent changes in cortical whisker representation in the adult mouse: a 2-deoxyglucose study

Sensory experience and learning can modify cortical body maps. We have previously reported that 3 days of classical conditioning, in which stimulation of a row of whiskers was paired with tail shock, produced an expansion of the cortical representation of the "trained row" labeled with 2-deoxyglucose (2DG), in layer IIIb and IV of the barrel cortex. The present study examined plastic remodelling of the vibrissal cortical representation after pairing whisker stimulation with a drop of sweet water. Cortical representations of rows of whiskers were mapped by 2DG autoradiography after 3 days and 2 months of training. The training resulted in enlargement of the cortical representation of vibrissae involved in the stimulus pairing compared with the contralateral representation of a row of whiskers, that were not touched during the training. This modification of whisker representation was different after short-term and long-term appetitive training. After three pairing sessions, changes in the width of cortical representation were visible in layers II/IIIa (29%) and layers V/VI (28%). After 2 months of training, significant changes in the width of cortical representation row B were found only in layer IV (41%). The changes were not observed in animals, that received whisker stimulation alone or in those who were subjected to training with unpaired stimuli. The results demonstrate that stimulus-pairing-induced changes in cortical whisker representation appeared with different time courses at different levels of cortical columnar information processing.

Sorting functional classes of evoked potentials by wavelets

Evoked potentials (EPs) recorded within the primary sensory cortex of non-anesthetized rats vary considerably with each peripheral stimulation. We have previously shown that most of this variance reflects the shift of cortical activation between habituated and aroused states. Here we show that a method of matching the potential's course by wavelet functions can reliably differentiate single EPs and may therefore, be used as a probe for indicating the current activation state of the cortex.

Identification of principal components in cortical evoked potentials by brief surface cooling

OBJECTIVES

The evoked potential recorded by a single electrode in rat's barrel cortex after whisker stimulation was shown to be composed of two main principal components shifted in time by about 3 ms. The purpose of this study was to verify the hypothesis that these components represent activity of supra- and infragranular pyramidal cell classes.

RESULTS

Our results show that a brief cooling pulse applied to the cortical surface abolishes the shorter latency component, which may therefore be attributed to the response of supragranular pyramidal cells.

CONCLUSIONS

The longer latency principal component, which disappears only with strong cooling pulses, is proposed to represent postsynaptic activity of infragranular pyramidal neurons.