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J A Larrauri

Publications and source records attributed to J A Larrauri.

4 recordsLinked to original sources
PubMed2006

Startle and prepulse inhibition as a function of background noise: a computational and experimental analysis.

Schmajuk and Larrauri [Schmajuk NA, Larrauri JA. Neural network model of prepulse inhibition. Behav Neurosci 2005;119:1546-62.] introduced a real-time model of acoustic startle, prepulse inhibition (PPI) and facilitation (PPF) in animals and humans. The model assumes that (1) positive values of changes in noise level activate an excitatory and a facilitatory pathway, and (2) absolute values of changes in noise level activate an inhibitory pathway. The model describes many known properties of the phenomena and the effect of brain lesions on startle, PPI, and PPF. The purpose of the present study is to (a) establish the magnitude of startle and PPI as a function of pulse, prepulse, and background intensity, and (b) test the model predictions regarding an inverted-U function that relates startle to the intensity of the background noise.

Acoustic Stimulation↗
PubMed2004

A pre-clinical study showing how dopaminergic drugs administered during pre-exposure can impair or facilitate latent inhibition.

RATIONALE: It has been suggested that, in classical conditioning, dopamine (DA) codes for (a) attention to the conditioned stimulus (CS) or (b) the intensity of the unconditioned stimulus. OBJECTIVES: To clarify the role of DA in pre-clinical classical conditioning studies. METHODS: An existing model of classical conditioning presented by Schmajuk, Lam, and Gray (J Exp Psychol Anim Behav Process 22:321-349, 1996) suggests that DA cells in the ventral midbrain area code for the attentionally modulated internal representation of the CS. It is assumed that this representation is increased by dopaminergic agonists and decreased by dopaminergic antagonists. Computer simulations with the model describe the effect of nicotine and haloperidol on latent inhibition. RESULTS: Simulations replicate experimental results demonstrating that both nicotine and haloperidol affect latent inhibition when administered during the pre-exposure phase. In addition, the model reproduces data showing that administration of nicotine or haloperidol results in the impairment or facilitation of latent inhibition depending on the duration of CS or the number of CSs. CONCLUSIONS: The model demonstrates that pre-clinical experimental results, including cell activity and pharmacological data, are consistent with an attentional role for DA in classical conditioning.

Computer Simulation↗
PubMed1999

Free radical scavenging capacity in the aging of selected red Spanish wines.

Free radical scavenging capacity by the DPPH(*) method and main physicochemical properties, polyphenols content by HPLC, color by a tristimulus colorimeter, and UV-vis spectra in the aging of selected red Spanish wines, were studied. As the wines age, they become darker (lower lightness, L) and increase their hue angle (lower red color) as well as the ratio of absorbance at 420 nm to that at 520 nm. Main polyphenolics identified in the samples were tannic acid, oenin, and gallic acid. The antiradical efficiency of the samples increased during aging, which could be related to an increase in the tannic acid concentration shown by the following correlationship: EC(50) = 1/(0.18 + 0.0011[tannic acid](mg/L)) with a correlation coefficient of 0.744.

Chromatography, High Pressure Liquid↗