Severe traumatic brain injury, frontal lesions, and social aspects of language use: a study of French-speaking adults

The purpose of this study was to gain insight into the social (pragmatic) aspects of language use by French-speaking individuals with frontal lesions following a severe traumatic brain injury. Eleven participants with traumatic brain injury performed tasks in three areas of communication: production (interview situation), comprehension (direct requests, conventional indirect requests, and hints), and metapragmatic knowledge. The results of the patients pointed out some strengths (turn-taking in production, and request comprehension, including hints and the speaker's intention) and some weaknesses (topic maintenance in production and metapragmatic knowledge). The patients' good comprehension of requests and their difficulty expressing metapragmatic knowledge suggest that they differ from controls in how they "explain the world": their knowledge of the event sequence was not based on verbally expressible knowledge about the relationship between the structural characteristics of a request utterance and those of its social production context. The pragmatic skills of persons with traumatic brain injury seem to vary across tasks: these individuals have specific strengths and weaknesses in different domains. In addition, marked interindividual differences were noted among the patients: three of them had only one weak point, topic maintenance. These interindividual differences were not systematically linked to performance on executive function tests, but lesion unilaterality (right or left) seems to help preserve patients' pragmatic and metapragmatic skills. The discussion stresses the need to take each patient's strengths and weaknesses into account in designing remediation programs.

LEARNING OUTCOMES

As a result of this activity, the reader will be able to explain the social/pragmatic aspects of language in typical and atypical participants with TBI. As a result of this activity, the reader will be able to identify social/pragmatic weaknesses and strengths.

Short- and long-term alterations of gene expression in limbic structures by repeated electroconvulsive-induced seizures

Rats were submitted to a series of 10 daily electroconvulsive shocks (ECS). A first group of animals was killed 1 day after the last seizure and a second group 30 days later. Tyrosine hydroxylase (TH) activity was measured using an in vitro assay in the nucleus caudatus, anterior cortex, amygdala, substantia nigra, ventral tegmental area, and locus ceruleus. The mRNA corresponding to this enzyme (TH-mRNA) was evaluated using a cDNA probe at the cellular level in the ventral tegmental area, substantia nigra, and locus ceruleus. Met-enkephalin (MET)-immunoreactivity and the mRNA coding for the preproenkephalin (PPE-mRNA) were assayed in striatum and the central nucleus of the amygdala. The day after the last ECS an increase of TH activity was observed in the ventral tegmental area, locus ceruleus, and substantia nigra in parallel with a similar increase in the amygdala and striatum; in the anterior cortex TH activity remained unchanged. TH-mRNA was increased in the locus ceruleus, evidencing the presence in this structure of a genomic activation. The amounts of MET and PPE-mRNA were unaffected in the striatum but increased in the amygdala. Thirty days after the last ECS we observed a decrease of TH activity in the amygdala and of TH-mRNA amount in the ventral tegmental area. In the locus ceruleus TH-mRNA remained higher in treated animals than in controls whereas TH activity returned to control levels. These results demonstrate that a series of ECS induces an initial increase of the activity of mesoamygdaloid catecholaminergic neurons followed by a sustained decrease through alterations of TH gene expression which could mediate the clinical effect of the treatment.

Release of [Met]enkephalin in the central nucleus of the amygdala is increased by application of potassium in the substantia nigra

Release of [Met]enkephalin immunoreactivity (Met-IR) in the central nucleus of the amygdala (ACE) was investigated in vivo in anesthetized rats implanted with push-pull cannulae. A stable spontaneous release of this peptide (1.3 fmol/15 min fraction) could be measured in the superfusates using a highly sensitive radioimmunoassay. The addition to the superfusion medium of cocktail of peptidase inhibitors increased three times the spontaneous release of the peptide. Superfusion with 30 mM potassium increased ten times the release of the peptide. Chemical stimulation of the substantia nigra with K+ enhanced four times the Met-IR release in the ipsilateral ACE. The dopaminergic component of the nigro-amygdaloid pathway appeared not to be directly implicated in this effect, since: d(+)amphetamine application in the ACE, which enhanced the local release of DA, remained without effect on Met-IR release and haloperidol-induced blockade of dopaminergic receptors in the ACE similarly did not affect Met-IR release.

Nigroamygdaloid dopamine neurons: nigral modulation of their activity

In order to study the mechanisms regulating the dopaminergic nigroamygdaloid cells, the release of dopamine was observed in the central nucleus of the amygdaloid complex. Halothane anesthetized rats were implanted, according to the experiment, with one or two push-pull cannulae in the central nuclei of the amygdala (ACE), the substantia nigra (SN) and/or the caudate nucleus (CN). Canulae were supplied with artificial cerebrospinal fluid (CSF) containing tritiated tyrosine, and labeled dopamine [3H]DA was evaluated in successive superfusate fractions. Electrical stimulation of the medial forebrain bundle with an implanted bipolar electrode induced an increase of the [3H]DA release in the ipsi- and contralateral ACE. Electrical stimulation of the SN produced only a very delayed effect in the ipsilateral ACE but an immediate and large increase of [3H]DA release in the contralateral structure. Superfusion of unlabeled DA and alpha-methyl-p-tyrosine in the SN remained ineffective on the [3H]DA release in the ipsilateral ACE. In this structure the release of [3H]DA was, however, decreased by nigral superfusion with gamma-amino-butyric acid (GABA). D-(+)-Amphetamine (1 microM), when superfused in the CN, induced a large enhancement of the [3H]DA release in the ipsilateral ACE simultaneously with the local increase of [3H]DA release. The results presented here are in agreement with the previous studies concerning the anatomical organization of the dopaminergic nigroamygdaloid pathway. The DA cell bodies located in the SN appear insensitive to a local action of DA, perhaps due to a lack of autoreceptors. They are, however, powerfully inhibited by GABA and the relation observed between the [3H]DA release in the CN and ACE support the hypothesis that the SN can act as a relay between the extrapyramidal and limbic systems.