Acute hyperammonaemia induces a sustained decrease in vigilance, which is modulated by caffeine.

UNLABELLED: Hyperammonaemia is observed after prolonged, intense exercise, or in patients with hepatic failure. In the latter, it is associated with a set of neurological and psychiatric abnormalities termed hepatic encephalopathy. THE AIMS OF OUR STUDY WERE: 1. to measure vigilance in a condition of induced hyperammonaemia; 2. to assess whether caffeine modulates the effects of hyperammonaemia on vigilance, if any. Ten healthy volunteers (28.5 ± 5 years; 5 males) underwent three experimental sessions consisting of two-hourly measurements of capillary ammonia, subjective sleepiness (Karolinska Sleepiness Scale) and vigilance (Psychomotor Vigilance Task, PVT), in relation to the intake of breakfast (+/-coffee), an amino acid mixture which induces hyperammonaemia (amino acid challenge; AAC), and AAC+coffee (only for participants who had coffee with their standard breakfast). The AAC resulted in: 1. the expected increase in capillary ammonia levels, with highest values at approximately 4 h after the administration; 2. a significant increase in subjective sleepiness ratings; 3. a sustained increase in PVT-based reaction times. When caffeine was administered after the AAC, both subjective sleepiness and the slowing in RTs were significantly milder than in the AAC-only condition. In conclusion, acute hyperammonaemia induces an increase in subjective sleepiness and a sustained decrease in vigilance, which are attenuated by the administration of a single espresso coffee.

Left hemisphere superiority for visuospatial functions in left-handers.

Male and female left- and right-handers have been tested with a divided visual field technique on a visuospatial (discrimination of angle width) and on a verbal task (vowel-consonant discrimination) using either a choice or a Go-No-go manual reaction time paradigm. Right-handers showed the expected pattern of hemispheric asymmetries with an advantage of the right hemisphere in the visuospatial task and an advantage of the left hemisphere in the verbal task. Such effects were statistically reliable only in male subjects. Left-handers, on the contrary, showed a different pattern of asymmetries. In the visuospatial task there was an overall superiority of the left hemisphere, while no hemispheric asymmetry was found in the verbal task.

Spatial sustained attention: better focused than divided?

Visuospatial attention was studied using three different reaction time tasks in a sustained attention paradigm (N = 35). Contrasting with findings from a phasic attention paradigm, our results suggest an equal ability to divide or focus sustained attention in the left and right fields in simple RT, a Go/No go-task, and choice RT.

Failure of hearing screening in high-risk neonates does not increase parental anxiety.

OBJECTIVE: The aim of this study was to determine whether a failure of neonatal hearing screening affected the anxiety level of parents of high-risk infants. METHODS: Two hundred and eighty-eight parents of infants included in the neonatal hearing screening protocol of our Institution were tested with the Spielberger State-Trait Anxiety Inventory and with an open-question questionnaire investigating parents' attitude to hearing problems in their child, done at the time of audiological follow-up. 105 were parents of high-risk infants who had been discharged from neonatal intensive care unit (NICU) and 183 of low-risk infants discharged from well-baby nursery. RESULTS: No differences in anxiety levels were seen between parents of high-risk infants passing and failing neonatal hearing screening using homogeneous case-control pairs. Additionally, no differences in the level of anxiety were found between parents of high- and low-risk infants failing neonatal auditory screening. CONCLUSIONS: Failure of neonatal auditory screening does not affect the anxiety levels of parents of high-risk infants at post discharge from NICU. This finding is a key factor to be considered when evaluating the costs and benefits of tests for universal neonatal hearing screening.

Modulation of a fronto-parietal network in event-based prospective memory: an rTMS study.

Event-based prospective memory (PM) is a multi-component process that requires remembering the delayed execution of an intended action in response to a pre-specified PM cue, while being actively engaged in an ongoing task. Some neuroimaging studies have suggested that both prefrontal and parietal areas are involved in the maintenance and realization of delayed intentions. In the present study, transcranial magnetic stimulation (TMS) was used to investigate the causal involvement of frontal and parietal areas in different stages of the PM process (in particular, target checking and intention retrieval), and to determine the specific contribution of these regions to PM performance. Our results demonstrate that repetitive TMS (rTMS) interferes with prospective memory performance when applied at 150-350 ms to the right dorsolateral prefrontal cortex (DLPFC), and at 400-600 ms when applied to the left posterior parietal cortex (PPC). The present study provides clear evidence that the right DLPFC plays a crucial role in early components of the PM process (target checking), while the left PPC seems to be mainly involved in later processes, such as the retrieval of the intended action.

Acquired stuttering: a motor programming disorder?

Acquired stuttering (AS) can follow unilateral right, left or bilateral hemispheric lesion, and can, but not necessarily, coexist with aphasia. In this paper we experimentally tested motor programming skills in a patient with AS of vascular origin. Motor programming consists in the structuration of the whole sequence of response prior to the onset of the first response element of a sequence of responses. Chronometric studies have shown that the time to initiate a sequence of manual responses is a function of the characteristics of the forthcoming sequence of responses. In our patient, reaction times involving single motor responses performed by right hand were within normal limit. On the contrary, when the task required a sequence of motor responses, there was a consistent difficulty in following the sequence: moreover, in the few correct sequences, reaction time analysis showed a lack of motor programming. It is suggested that AS could be the speech epiphenomenon of a more generalized disturbance of motor programming.

Naming disorders and semantic representations.

The status of semantic conceptual structures in aphasia was investigated with relation to naming disorders in spontaneous and constrained speech production. A battery of six tasks was administered to 25 control subjects and 25 aphasics: spontaneous speech production (from which the percentage of nouns was calculated), confrontation naming, understanding class relationships (verbal and pictorial), and understanding thematic relationships (verbal and pictorial). Results indicated the important role of taxonomic abilities for naming, while other conceptual structures (i.e., thematic relations) do not seem to play any important role in the process of naming. These results are discussed in terms of the internal organization of semantic information.

Impairment in processing meaningless verbal material in several modalities: the relationship between short-term memory and phonological skills.

Phonological processing abilities were studied in a patient who, following focal brain damage, showed selective impairment in non-word reading, writing, and repetition and also a severe short-term memory (STM) deficit specific for auditorily presented verbal material. The patient could execute tasks involving phonemic manipulation and awareness perfectly. Our data, in contrast with earlier observations in a case of developmental phonological dyslexia, show that acquired impairment in non-word reading, writing, repetition, and immediate memory may occur despite good phonological processing abilities. The role of STM in processing meaningless verbal material is discussed.

Neuropsychological evaluation of neurologically asymptomatic HIV-infected children.

Forty-two children born to HIV positive mothers (29 infected at different stages of the disease, according to the Disease Control Classification Centers, and 13 noninfected) underwent evaluation using a battery of neuropsychological tests. Executive function impairments were present in all infected children, whereas memory and visuo-prassic deficits were evident only in those with full-blown AIDS. Language abilities and overall intelligence were spared. Performance of seroreverters was in the normal range. These findings suggest that even in neurologically asymptomatic children, neuropsychological evaluation can identify early impairment of specific cognitive functions. The findings are discussed in the light of the prognostic power of neuropsychological assessment for early signs of HIV neurological involvement.

Planning times during traveling salesman's problem: differences between closed head injury and normal subjects.

We studied planning behavior in a group of normal subjects and a group of closed head injury patients (CHI). A computerized version of the traveling salesman's problem was used as a visuospatial planning ability task. The program collected measurements of partial times, number of moves, and number of skipped subgoals. These measures allow us to calculate a "planning index" of subjects' planning ability. Results show that CHI patients present limitations in the planning process due to the lack of ongoing planning.