The auditory sensory memory trace decays rapidly in newborns

The present study investigated the temporal dynamics of auditory sensory memory in newborns as reflected by the mismatch negativity (MMN), a preattentive electric change-detection response. MMN was obtained from 24 full-term healthy newborns who were either awake or asleep (quiet or active sleep) during the experiments. Stimuli were 1,000 Hz tones (standards) that were occasionally replaced by 1,100 Hz tones (deviants). The constant stimulus onset asynchrony (SOA) was, in separate blocks, either 450, 800, or 1,500 ms. A prominent MMN was obtained at the 800 ms SOA in all three sleep or waking states, whereas no MMN occurred at 450 and 1,500 ms SOAs. In view of the fact that in adults MMN is elicited even with a 10s SOA, these results imply that the time span of auditory memory is considerably shorter in neonates than in adults and 8-12-year-old children.     

Role of dopamine,the frontal cortex and memory circuits in drug addiction: insight from imaging studies

Drug addiction is characterized by a set of recurring processes (intoxication, withdrawal, craving) that lead to the relapsing nature of the disorder. We have used positron emission tomography to investigate in humans the role of dopamine (DA) and the brain circuits it regulates in these processes. We have shown that increases in DA are associated with the subjective reports of drug reinforcement corroborating the relevance of drug-induced DA increases in the rewarding effects of drugs in humans. During withdrawal we have shown in drug abusers significant reductions in DA D2 receptors and in DA release. We postulate that this hypodopaminergic state would result in a decreased sensitivity to natural reinforcers perpetuating the use of the drug as a means to compensate for this deficit and contributing to the anhedonia and dysphoria seen during withdrawal. Because the D2 reductions are associated with decreased activity in the anterior cingulate gyrus and in the orbitofrontal cortex we postulate that this is one of the mechanisms by which DA disruption leads to compulsive drug administration and the lack of control over drug intake in the drug-addicted individual. This is supported by studies showing that during craving these frontal regions become hyperactive in proportion to the intensity of the craving. Craving is also associated with activation of memory circuits including the amygdala (implicated in conditioned learning), hippocampus (implicated in declarative learning), and dorsal striatum (implicated in habit learning) all of which receive DA innervation. We therefore postulate that dopamine contributes to addiction by disrupting the frontal cortical circuits that regulate motivation, drive, and self-control and by memory circuits that increase the motivational salience of the drug and drug-associated stimuli.     

Working memory retention systems: a state of activated long-term memory

High temporal resolution event-related brain potential and electroencephalographic coherence studies of the neural substrate of short-term storage in working memory indicate that the sustained coactivation of both prefrontal cortex and the posterior cortical systems that participate in the initial perception and comprehension of the retained information are involved in its storage. These studies further show that short-term storage mechanisms involve an increase in neural synchrony between prefrontal cortex and posterior cortex and the enhanced activation of long-term memory representations of material held in short-term memory. This activation begins during the encoding/comprehension phase and evidently is prolonged into the retention phase by attentional drive from prefrontal cortex control systems. A parsimonious interpretation of these findings is that the long-term memory systems associated with the posterior cortical processors provide the necessary representational basis for working memory, with the property of short-term memory decay being primarily due to the posterior system. In this view, there is no reason to posit specialized neural systems whose functions are limited to those of short-term storage buffers. Prefrontal cortex provides the attentional pointer system for maintaining activation in the appropriate posterior processing systems. Short-term memory capacity and phenomena such as displacement of information in short-term memory are determined by limitations on the number of pointers that can be sustained by the prefrontal control systems.     

Machiavellianism and Theory of Mind in people affected by schizophrenia

CONTEXT: People affected by schizophrenia show deficits in social interaction (Cramer, Bowen, & O'Neill, 1992); such a deficit may stem from an alteration in the representation of mental states. OBJECT: In this study we have examined 42 people affected by schizophrenia, diagnosed according to DSM-IV criteria, by testing them with an instrument (the Mach IV scale, Christie & Geis, 1970) assessing "Machiavellian Intelligence" according to Niccolò Machiavelli's assertions. Schizophrenic subjects were compared to a sample of normal controls, matched for age, sex, and education. OBJECTIVE: The aim of our study was to evaluate if there were correlations between the ability to understand other people's mental states and the capacity for interpreting "Machiavellian expressions." RESULTS: Results show that people affected by schizophrenia are less able to use Machiavellian-style "tactical" abilities than controls. CONCLUSION: Such a disability seems to be correlated to poor mentalising abilities.     

Food for Boys and Food for Girls: Do Preschool Children Hold Gender Stereotypes about Food?

Sex Roles - Family meals are occasions for socializing children to gender roles and the symbolic meaning of food and eating. One of the relevant symbolic meaning of food concerns its gender...     

Widening the temporal window: processing support in the treatment of aphasic language production

Investigations of language processing in aphasia have increasingly implicated performance factors such as slowed activation and/or rapid decay of linguistic information. This approach is supported by studies utilizing a communication system (SentenceShaper) which functions as a "processing prosthesis." The system may reduce the impact of processing limitations by allowing repeated refreshing of working memory and by increasing the opportunity for aphasic subjects to monitor their own speech. Some aphasic subjects are able to produce markedly more structured speech on the system than they are able to produce spontaneously, and periods of largely independent home use of SentenceShaper have been linked to treatment effects, that is, to gains in speech produced without the use of the system. The purpose of the current study was to follow up on these studies with a new group of subjects. A second goal was to determine whether repeated, unassisted elicitations of the same narratives at baseline would give rise to practice effects, which could undermine claims for the efficacy of the system.