Biomedical subjects

Carlos Tomaz

Publications and source records attributed to Carlos Tomaz.

23 records · Page 2Linked to original sources

PubMed2002

Effect of practice on hand preference on a color visual discrimination task by capuchin monkeys (Cebus apella).

Effects of practice on hand preference in nonhuman primates have indicated an initial right-hemispheric advantage in new tasks that can be reversed or disappear after a long period of training. The aim of this study was to examine the effects of 6-mo. practice on hand preference in capuchin monkeys (Cebus apella) performing a color visual discrimination task which requires attention and learning or memory processes. For this purpose, an early period of practice (first 200 trials) was compared with a late period of practice (the last 200 trials after 6 mo. practice). No population-level biases were observed between the use of hands either early in training or after 6 mo. of practice. Individual analysis indicated that two of the five subjects tested strengthened their initial hand preference but three subjects changed their preference with the practice. No correlation was observed between hand use and performance. These results suggest that hand preference in capuchin monkeys can be influenced by practice and is not only a direct function of hemispheric specialization.

Animals↗

PubMedDate not supplied

Injections of botulinum toxin type a produce pain alleviation in intractable trigeminal neuralgia.

To report the effects of local injections of botulinum toxin type A regarding pain relief and long-term control in a patient with intractable trigeminal neuralgia. The patient was a 75-year-old man with trigeminal neuralgia in the left hemifacial region. His pain was unbearable and could not be controlled by carbamazepine, amitriptyline, or blocked by infiltration of a glycerol solution or phenol. The authors evaluated pain intensity, quality, and location using a Visual Analog Scale to establish the efficacy of botulinum toxin type A injections. Two units of botulinum toxin type A (Botox) were subcutaneously injected once in eight points distributed along the territory of V1 and V2. Visual Analog Scores were measured at baseline and at 7, 30, 60, and 90 days after treatment. The authors also examined the patient's general condition and daily life activities. The Visual Analog values were, respectively, 82, 54, 25, 25, and 45 mm at each follow-up examination. No side effects were observed on the site of injection and on the patient's clinical state. The authors have been able to reduce trigeminal neuralgia pain with botulinum toxin type A injections in the V1, V2 territory during all the period of study, as well as to withdraw all medication. Interestingly, there was concomitant reduction of pain also in V3, which was not injected.

Aged↗

PubMedDate not supplied

Differences in aerial and terrestrial visual scanning in captive black tufted-ear marmosets (Callithrix penicillata) exposed to a novel environment.

Aerial and terrestrial visual scanning were investigated in captive black tufted-ear marmosets, Callithrix penicillata, exposed to a novel environment. Naive adult subjects (n=24) were individually exposed to a figure-eight maze during seven 30-min trials, 48 h apart. Habituation to the maze was observed, as indicated by the significant decrease in locomotion. The frequency of aerial scanning, however, remained elevated throughout the 7 trials, while its duration rapidly increased to high levels. Frequency and duration of terrestrial scanning persisted at constant low rates, differing significantly from aerial scanning. Males and females did not differ significantly. The different impact of aerial versus terrestrial predators could have a significant influence on vigilant behaviour in this species. Thus, visual scanning is an important and highly organized antipredation strategy in marmosets.

Animals↗

PubMedDate not supplied

Colour discrimination in the black-tufted-ear marmoset (Callithrix penicillata): ecological implications.

The dietary diversity of marmosets is substantial, which may reflect differences in their colour vision. This study examined the colour discrimination ability of a gummivore/insectivore callitrichid, Callithrix penicillata, which inhabits the Brazilian cerrado (bush savanna). A series of ecologically relevant tasks, involving a behavioural paradigm of discrimination learning in semi-natural conditions and the usage of ecologically relevant stimuli, was executed. Three marmosets, 2 males and a female, behaved like human dichromats, showing an impaired performance when orange and green stimuli had to be discriminated. In contrast, 2 females resembled human trichromats, discriminating those kinds of pairs. Our data suggest that Callithrix penicillata presents a polymorphic trichromacy, with dichromatic males and dichromatic or trichromatic females.

Animals↗

PubMedDate not supplied

Declarative memory retention and emotional stimuli. A study of an Italian sample.

Psychological and pharmacological studies in humans suggest that emotional arousal enhances long-term memory. In this paper we used, in an Italian sample, an adaptation of a paradigm previously utilized in American samples to study the relationship between emotion and long-term memory. Seventy-two healthy adults from different educational backgrounds were randomly assigned either to a neutral group or to an emotional arousal group and then told a short story, presented audio-visually. In both groups, the slides shown and the slide sequence were the same, and the images were accompanied by a narrative. The two versions of the story differed primarily in their emotional content. Shortly after viewing the slide presentation, the participants were asked to rate the emotionality of the narrative, and ten days later were submitted to a retention test. The emotionally-arousing version of the story was rated as more emotional than the neutral one. Compared with the members of the neutral group, the subjects in the arousal group recalled a significantly higher number of elements from the story. There was no overall difference between the two groups in performance on the recognition memory test. These results confirm that the emotional content of stimuli enhances long-term declarative memory of those stimuli, and indicate the possible usefulness of applying the paradigm utilized in this study to different clinical samples from various cultural backgrounds.

Adolescent↗