Biomedical subjects

J Cudeiro

Publications and source records attributed to J Cudeiro.

23 records · Page 2Linked to original sources

PubMed1993

Influence of layer V of area 18 of the cat visual cortex on responses of cells in layer V of area 17 to stimuli of high velocity.

Focal blockade of restricted regions in layer V of area 18 was used to assess the contribution of this region to the responses to high-velocity stimuli of cells in retinotopically matched, layer V in area 17. In 40% of cases, blockade within area 18 revealed responses of area 17 cells to high-velocity stimuli to which they previously showed only poor responses. Stimulus specificity of the cells in area 17 was otherwise unaltered. All effects were reversible and repeatable. We suggest that a component of the output of layer V from area 18 normally suppresses the responses of retinotopically matched cells within area 17 to stimuli of high velocity, thereby enhancing the specificity of those cells to stimuli of low velocity.

Animals↗

PubMed1990

Lateral-posterior and pulvinar reaching cells--comparison with parietal area 5a: a study in behaving Macaca nemestrina monkeys.

In a previous study we have demonstrated the existence of pulvinar (puv) cells which were optimally activated when a monkey executed reaching movements with his limbs (Acuña et al 1983). We now describe further observations in four Macaca nemestrina monkeys trained to perform goal directed reaching movements aimed at four different positions in space. Extracellular unit activity in the lateralis posterior (lp) and puv nuclei, together with electrooculograms were recorded during the execution of the task. Seven hundred and sixty neurons were studied in the lp-puv complex. One hundred and twenty three cells (16%) showed changes in activity related to the reaching movements. Reaching related cells fell into two categories: goal direction sensitive (28/123 = 23%) and pandirectional (95/123 = 77%). Goal direction sensitive cells showed different responses depending on the direction of the goal relative to the starting point of the movement. The responses of the pandirectional cells were independent of goal direction. The activity of the remaining cells (637/760) could not be correlated with reaching movements. In a smaller number of area 5a (PE) cells (n = 109) studied in one monkey, 82 (75%) were classified as reaching related cells. Of these, 76% (62/82) were goal direction sensitive and 24% (20/82) pandirectional. The lp-puv cells were more dependent on the intentionality of movement than area 5a cells, and not reliably activated by passive manipulation of the limb. After injection of HRP-WGA in area 5a, where the reaching cells were recorded, labeled cells and terminals were located in the lp-puv zones where reaching cells were also found.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Does the pulvinar-LP complex contribute to motor programming?

Extracellular unit recording studies in the pulvinar lateral posterior complex (Pul-LP) of behaving monkeys have shown a response property not previously reported. In monkeys performing aimed arm reaching movements towards frontally located targets some cells showed a change in activity beginning 495 +/- 84 ms before the onset of the reaching movement. This change in frequency precedes that observed in primary motor and parietal posterior cortex for reaching movements. These findings seem to indicate the involvement of the Pul-LP in motor functions and suggest its possible contribution to motor programming.

Action Potentials↗

PubMed1986

Lateral-posterior (LP) and pulvinar unit activity related to intentional upper limb movements directed to spatially separated targets, in behaving Macaca nemestrina monkeys.

We have showed in a previous paper that the pulvinar extracellular unit activity in behaving monkeys was dependent on the attention the animal paid to the stimulus, or on its behavioral significance or on the intentional movements the animal performed. Several groups of pulvinar cells quantitatively studied in the behavioral tasks the monkeys performed were described. "Projection and hand manipulation" neurons belong to a group of pulvinar cells that increased their activity when the animal made an intentional movement of the limb towards an object that attracted his attention. Some of these cells showed temporal patterns of discharge as well as peak rates of activity that frequently differed for reaching movements to spatially separated targets. This suggested that the overall pattern of discharge of these population of cells differ for different directions of arm movements. We give here a description of the observations made in three behaving Macaca Nemestrina monkeys trained to project there hands and arms to four spatially separated targets situated on a panel in front of them and at arm's reach. The extracellular unit activity in the LP-pulvinar was simultaneously recorded during the execution of the behavioral task. Statistical analysis were applied to objectively quantify the electrophysiological data. In 39 microelectrode penetrations, 362 neurons were recorded. 50 cells, a 13 p. 100, showed significative changes in their discharge during the execution of the task. Neurons of this class were activated when the monkey made an intentional movement with his upper limb towards something that attracted his attention. They were driven very poorly, and in a not easily reproducible way by passive manipulation of the limb.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

[How does the brain wake up? The nitric oxide blow].

INTRODUCTION: A synthesis of the role of the neuromodulator nitric oxide (NO) on the sleep-wake cycle control is made, emphasizing the function of the activating ascending pathways implicated in arousal. DEVELOPMENT: There are some hypotheses regarding the role of sleep: memory consolidation, ecological factors, cellular repair and nervous system development. The sleep-wake cycle is an active process, modulated by subcortical regions (mesopontine nuclei, diencephalon and basal forebrain) with connections and reciprocal interactions among them. NO is released by neurons and terminals of the sleep-wake cycle modulatory nuclei. The role of NO in this cycle is mainly linked to activation processes: transition to and maintenance of waking and rapid eye movement (REM) sleep. At thalamic level NO is released by cholinergic fibers of the mesopontine nuclei and induces a facilitation of neural responses. In the basal forebrain there exists NO in the cholinergic cells contacting the cortex, suggesting that this ascending pathway can also collaborate in cortical activation through the release of NO. CONCLUSIONS: NO has been identified in neurons of the brain areas controlling the modulation of arousal; hence, this gaseous neuromodulator can have an essential function promoting a quick and global activation of cortical neurons.

Brain↗