CS-specific gamma,theta, and alpha EEG activity detected in stimulus generalization following induction of behavioral memory by stimulation of the nucleus basalis

Tone paired with stimulation of the nucleus basalis (NB) induces behavioral memory that is specific to the frequency of the conditioned stimulus (CS), assessed by cardiac and respiration behavior during post-training stimulus generalization testing. This paper focuses on CS-specific spectral and temporal features of conditioned EEG activation. Adult male Sprague-Dawley rats, chronically implanted with a stimulating electrode in the NB and a recording electrode in the ipsilateral auditory cortex, received either tone (6kHz, 70dB, 2s) paired with co-terminating stimulation of the nucleus basalis (0.2s, 100Hz, 80-105 microA, ITI approximately 45s) or unpaired presentation of the stimuli (approximately 200 trials/day for approximately 14 days). CS-specificity was tested 24h post-training by presenting test tones to obtain generalization gradients for the EEG, heart rate, and respiration. Behavioral memory was evident in cardiac and respiratory responses that were maximal to the CS frequency of 6kHz. FFT analyses of tone-elicited changes of power in the delta, theta, alpha, beta1, beta2, and gamma bands in the paired group revealed that conditioned EEG activation (shift from lower to higher frequencies) was differentially spectrally and temporally specific: theta, and alpha to a lesser extent, decreased selectively to 6kHz during and for several seconds following tone presentation while gamma power increased transiently during and after 6kHz. Delta exhibited no CS-specificity and the beta bands showed transient specificity only after several seconds. The unpaired group exhibited neither CS-specific behavioral nor EEG effects. Thus, stimulus generalization tests reveal that conditioned EEG activation is not unitary but rather reflects CS-specificity, with band-selective markers for specific, associative neural processes in learning and memory.     

When Good Intentions Are Not Enough: Modeling Postdecisional Cognitive Correlates of Condom Use1

Measures of intention usually leave substantial proportions of the variance in behavior unexplained. It has been suggested that improved behavioral prediction could be achieved by identifying postdecisional cognitive processes capable of distinguishing between intenders who do act and those do not act. Condom-related self-report measures of postdecisional cognitive processes were developed and tested in a cross-sectional questionnaire study involving 447 heterosexual students. A discriminant function composed of postdecisional measures was found to significantly distinguish between intenders who reported use and non-use and to correctly classify 80% of intenders. The results indicate that measures of the relative importance of competing intentions, prior planning of specific preparatory actions, and action-specific self-efficacy may enhance the prediction of condom use among intenders.     

Establishing global and local correspondence between successive stimuli: the holistic nature of backward alignment

Reflection decisions on alphanumeric characters display systemic effects of disorientation, suggesting that subjects mentally rotate the stimulus to the upright (the uprighting process). However, response time also increases with increasing angular disparity between the current and preceding orientations. This occurs only when the current stimulus is brought into congruence with the preceding one (the backward alignment process). In the present study, we examined the hypothesis that the transformation that occurs in backward alignment in holistic even in tasks in which the uprighting process is likely to be piecemeal. Evidence supporting this hypothesis is presented on the basis of tasks requiring either classification of numbers (Experiments 1 and 3) and words (Experiment 2), or mirror image discrimination on letter pairs (Experiment 4). The results indicated that backward alignment establishes global correspondence between successive stimuli and is indifferent to local correspondence at the level of the constituent elements. The establishment of this global correspondence decreases with the number of elements in the stimulus (Experiment 5), but its effects are still observed for four-letter strings (Experiment 6).     

The detectability of geometric structure in rapidly changing optical patterns.

Human vision is sensitive to the coherent structure and motion of simple dot patterns undergoing rapid random transformations, even when the component dots are widely separated spatially. A study is reported in which visual sensitivity to translations, rotations, expansions, pure shear, and additive combinations of these transformations was investigated. Observers discriminated between coherent (correlated) movements, in which all the component dots moved simultaneously in corresponding directions and distances, and incoherent (uncorrelated) movements, in which the movements of individual dots were statistically independent. In experiment 1 the accuracy of coherence discrimination was found to be similar for all four of the basic transformations and to increase linearly with the distance of the movements. The discriminability of coherent versus incoherent motion was also found to be similar to the detectability of any motion, suggesting that concurrent movements of individual dots are visually interrelated. In experiments 2 and 3 the visual independence of these four groups of transformations was tested by comparing the accuracy of coherence discrimination of each of the transformations presented alone with that when added to background motions produced by each of the four transformations. Coherence discriminations were less accurate when the target transformation was added to another background transformation, indicating that these transformations are not visually independent. Rotations and expansions, however, were visually independent. In experiment 3 qualitatively similar effects for patterns of several different sizes and dot densities were found. In general, an impressive visual sensitivity to globally coherent structure and motion under several different geometric transformations was observed in these experiments. A basic theoretical issue concerns the local visual mechanisms underlying this sensitivity.     

The discriminability of smooth stereoscopic surfaces.

In this study the sensitivity of human vision to the smoothness of stereoscopic surface structure was investigated. In experiments 1 and 2 random-dot stereograms were used to evaluate the discrimination of smooth versus 'noisy' sinusoidal surfaces differing in the percentages of points on a single smooth surface. Fully coherent smooth surfaces were found to be much more discriminable than other less smooth randomly perturbed surfaces. In experiment 3 the discrimination between discontinuous triangle-wave surfaces and similarly shaped smoothly curved surfaces obtained from the addition of the fundamental and the third harmonic of the corresponding triangle-wave surface was evaluated. The triangle-wave surfaces were found to be more accurately discriminated from the smoothly curved surfaces than would be predicted from the detectability of the difference in their Fourier power spectra. This superior discriminability was attributed to differences between the curvature and/or discontinuity of the two surfaces. In experiment 3 the effects of incoherent 'noise' points on the discrimination between the two surface types were also evaluated. These randomly positioned noise points had a relatively small effect on the discrimination between the two surfaces. In general, the results of these experiments indicate that smooth surfaces are salient for stereopsis and that isolated local violations of smoothness are highly discriminable.     

COMMONALITY OF WORD LISTING,PREDICTABILITY, ORIGINALITY AND CHUNKING

Les AA. analysent les données de deux épreuves verbales (liste de mots, créativité) auxquelles ont été soumis des adolescents hindous (N = 144) et américains (N = 96). Ils constatent que : (1) les sujets hindous montrent plus de variabilité dans la tendance à donner des mots identiques (commonality) dans une liste et se caractérisent par un nombre plus élevé de “ groupes ” de mots, liés entre eux dans une même chaîne de pensée; (2) les filies donnent plus de mots identiques que les garçons, mais seulement dans le groupe américain; (3) il existe une relation faible, mais de sens contraire, entre la prédictibilité et le groupement des mots dans les deux groupes linguistiques. La discussion est centrée sur la pertinence des ressemblances plutôt que des différences en matière de comparaisons interculturelles; les similitudes verbales pourraient refléter chez les sujets américains L'orientation vers le groupe des pairs et il est possible de donner d'autres explications à L'absence de Jiaison entre les similitudes verbales, la prédictibilité, I'originalité et la tendance à répondre par groupes de mots.