Treatment dynamics in sensorimotor disorders: the contribution of electrophysiology]

In the field of sensorimotor activities, progresses achieved over the last fifty years have been largely driven by the Reaction Time (RT) paradigm. Information processing models are set in the context of a global breakdown of sensorimotor activities in multiple concatenated stages, each aggregated in many fundamental operations that are functionally linked. If there is a consensus today about this breakdown, the way stages organize themselves in time however is still much debated. According to one hypothesis, there is no temporal overlap between each stages: the process occurs sequentially. According to another theory, the stages overlap over in time: the process occurs in a parallel manner. A behavioral analysis does not allow to determine between these two hypothesis because the RT represents the final product of the whole sensorimotor pathway, while the temporal organization of the processing of information depends on the nature of the transfer between individual stages. An all-or-nothing information transfer, also called discrete, leads to a sequential organization, while a progressive or continuous transfer brings about a parallel organization. Moreover, contrary to a preconceived notion, data obtained from classical neurophysiology are compatible with both a sequential organization and a parallel organization. Particularly, the great number of connections between the different elements of the nervous system has often seemed difficult to conciliate with a sequential organization. In fact, this argument is inadmissible because it stems from confusion between a temporal organization and an anatomical organization of the processing of information. More generally, our knowledge of the functional anatomy of sensorimotor activities imposes but few constraints on the temporal organization patterns of the processing of information. The lack of interest for the neurophysiological argument seems essentially due to the fact that theses arguments rest on research which is not aimed at the temporal organization of the sensorimotor information processing. Recently, approaches that integrate concepts and methods used in experimental psychology and neurosciences have contributed to putting in perspective the organization of information processing. Electromyography, EEG, reflexology and neuronal recording techniques have been used in the context of two inference logics. The first logic, that we call "factual", is based on the study of functional relations between RT and certain neuronal events. The second logic, that we call "chronometric", is based on the study of the relationships between RT and intervals resulting from the breakdown of the RT in relation to certain neuronal events. Generally speaking, most studies suggest that in tasks where the stimulus is composed of numerous attributes, information processing operates in parallel. On the other hand, when the stimulus is made up of a single attribute, information processing could be operating in a sequential manner. One weakness of this electrophysiological approach is that it has so far only examined relationships between physiological indicators and means RT. We propose here to offset these weaknesses by examining functional relationships between RT distribution variances and certain neuronal events linked to information processing.     

Involvement of the medial prefrontal cortex in two alternation tasks using different environments

Spatial alternation performance in rats is usually evaluated with the T-Maze. The first aim of this study was to analyze the effect of a selective lesion of medial prefrontal cortex (mPFC) on performance in a T-maze. Second, we wanted to validate a new test using alternation in a water maze (AWM). The mPFC of 21 male Sprague-Dawley rats was lesioned bilaterally using in situ microinjection of ibotenic acid. Thirteen control rats received injections of the vehicle only. Results show that mPFC lesioned rats were significantly impaired in the T-Maze as well as in the AWM compared to controls. These results validate the AWM as a frontal cortex dependent task probing working memory and/or behavioral flexibility. We suggest that the AWM may be more powerful than the T-maze as an investigational tool, given that is can be easily compared to other water maze tasks that evaluate other (nonfrontal) cognitive modules.     

Application of stochastic modeling to the assessment of group and individual differences in cognitive functioning

This article begins with a guiding schema of relations among cognitive science, clinical science, and assessment technology. Emphasis is placed on stochastic modeling of cognitive processes. Basic models are adjusted so as to parsimoniously accommodate performance deviations occurring with psychopathology. Modified portions of models indicate functions affected by disorder, whereas portions remaining intact indicate spared functions. Findings from clinical cognitive science are applied to the individual case using Bayesian procedures. Methods are instantiated with respect to cognitive psychopathology of paranoid schizophrenia. The authors address observations and issues arising from this application, including integration of these methods with current assessment practices.     

Effects of attitude action identification on congruence between attitudes and behavioral intentions toward social groups

Attitude Representation Theory (ART) holds that attitude-relevant responses are informed by mental representations of the attitude object, which include the individual's actions toward that object. Action Identification Theory (AIT) holds that the same action can be identified at multiple levels. Individuals who identify their actions at lower levels have less flexibility in how they perform the action, and thus enact the action less consistently. An integration of ART and AIT suggested that individuals who spontaneously (Experiment 1) or through manipulation (Experiments 2 and 3) identify their attitude-relevant actions toward a social group at lower levels might display less attitude-intention congruence than would individuals who identify their attitude-relevant actions at higher levels. ART and AIT are discussed as having links with each other and with other theories of attitude and judgment processes.     

Oral administration of guanosine impairs inhibitory avoidance performance in rats and mice

Extracellular guanine-based purines, mainly the nucleoside guanosine, have recently been shown to exert neuroprotective effects, which seem to be related to antagonism of the glutamatergic system. In this study, we investigated the effects of acute oral administration of guanosine on inhibitory avoidance task in rats and mice. We also studied its effects on locomotor activity, anxiety-related behaviors and mechanisms of action involving the purinergic system. Guanosine (2.0 and 7.5mg/kg, per os), administered 75min pretraining, dose-dependently impaired retention of the inhibitory avoidance task in rats and mice, an effect not prevented by the adenosine receptor antagonist caffeine. Guanosine presented no effects on locomotor activity and anxiety-related behaviors. This amnesic effect of guanosine may be compatible with inhibition of glutamatergic system and seems to be not mediated by adenosine.     

Classical conditioning of eyelid and mystacial vibrissae responses in conscious mice

The murine vibrissae sensorimotor system has been scrutinized as a target of motor learning through trace classical conditioning. Conditioned eyelid responses were acquired by using weak electrical whisker-pad stimulation as conditioned stimulus (CS) and strong electrical periorbital stimulation as unconditioned stimulus (US). In addition, conditioned vibrissal protraction was obtained pairing either weak electrical whisker-pad stimulation or a tone as CS, with a strong electric shock delivered in the whisker-pad as US. This finding suggests that evolutionary pressure has selected a sensorimotor system capable of constructing conditioned responses on the basis of temporal relationships of stimuli, independently of any putative functional purpose.     

Neurobiological and endocrine correlates of individual differences in spatial learning ability

The polysialylated neural cell adhesion molecule (PSA-NCAM) has been implicated in activity-dependent synaptic remodeling and memory formation. Here, we questioned whether training-induced modulation of PSA-NCAM expression might be related to individual differences in spatial learning abilities. At 12 h posttraining, immunohistochemical analyses revealed a learning-induced up-regulation of PSA-NCAM in the hippocampal dentate gyrus that was related to the spatial learning abilities displayed by rats during training. Specifically, a positive correlation was found between latency to find the platform and subsequent activated PSA levels, indicating that greater induction of polysialylation was observed in rats with the slower acquisition curve. At posttraining times when no learning-associated activation of PSA was observed, no such correlation was found. Further experiments revealed that performance in the massed water maze training is related to a pattern of spatial learning and memory abilities, and to learning-related glucocorticoid responsiveness. Taken together, our findings suggest that the learning-related neural circuits of fast learners are better suited to solving the water maze task than those of slow learners, the latter relying more on structural reorganization to form memory, rather than the relatively economic mechanism of altering synaptic efficacy that is likely used by the former.     

Influence of metacognitive variables and thought suppression on number of thoughts, discomfort they produce and number and quality of auditory illusions

Based on the model proposed by Morrison, Haddock & Tarrier (1995) on auditory hallucinations, this study explores the relationships between certain metacognitive variables and number of thoughts, the discomfort they produce, number of auditory illusions and the quality with which they are perceived in a sample from a non-clinical population. After group administration of the Metacognitions Questionnaire, 61 participants were randomly assigned to a suppression group (n = 31) or a focalization group (n = 30) in relation to thoughts with different degrees of self-discrepancy. Forty-eight hours after the set task, a non-vocal auditory stimulus was presented, and subjects were required to say whether they heard any words and, if so, how clearly. The results show how the metacognitive factors studied are useful for predicting our findings only for the suppression group and not for that of focalization. These data are discussed in the light of Morrison et al.'s model of auditory hallucinations.