Neural mechanisms of infant learning: differences in frontal theta activity during object exploration modulate subsequent object recognition

Investigating learning mechanisms in infancy relies largely on behavioural measures like visual attention, which often fail to predict whether stimuli would be encoded successfully. This study explored EEG activity in the theta frequency band, previously shown to predict successful learning in adults, to directly study infants'' cognitive engagement, beyond visual attention. We tested 11-month-old infants (N = 23) and demonstrated that differences in frontal theta-band oscillations, recorded during infants'' object exploration, predicted differential subsequent recognition of these objects in a preferential-looking test. Given that theta activity is modulated by motivation to learn in adults, these findings set the ground for future investigation into the drivers of infant learning.     

Precisely timed oculomotor and parietal EEG activity in perceptual switching

Blinks and saccades cause transient interruptions of visual input. To investigate how such effects influence our perceptual state, we analyzed the time courses of blink and saccade rates in relation to perceptual switching in the Necker cube. Both time courses of blink and saccade rates showed peaks at different moments along the switching process. A peak in blinking rate appeared 1,000 ms prior to the switching responses. Blinks occurring around this peak were associated with subsequent switching to the preferred interpretation of the Necker cube. Saccade rates showed a peak 150 ms prior to the switching response. The direction of saccades around this peak was predictive of the perceived orientation of the Necker cube afterwards. Peak blinks were followed and peak saccades were preceded by transient parietal theta band activity indicating the changing of the perceptual interpretation. Precisely-timed blinks, therefore, can initiate perceptual switching, and precisely-timed saccades can facilitate an ongoing change of interpretation.     

Individual alpha activity of electroencephalogram and nonverbal creativity

The main objective of present correlational investigation was to clarify relationships between nonverbal creativity indices and individual electroencephalogram alpha activity indices: individual alpha peak frequency, alpha band width, magnitude of alpha desynchronization and alpha spindle indices such as duration, amplitude, variability and skewness. The EEG was recorded in 98 healthy male right-handed subjects. Scores of nonverbal creativity (i. e., fluency, originality, and flexibility) were assessed using the Torrance test of nonverbal performance. The study showed that fluency in creative performance was associated with individual alpha peak frequency and alpha spindles duration, whereas originality and plasticity--with individual alpha band width and spindle amplitude variability. The findings also show that both highest and lowest individual alpha peak frequency indices are associated with enhanced scores of originality. It is suggested that individual alpha activity indices could be presented as individual predictors of fluency, plasticity and originality of nonverbal creativity.     

Individual differences in brain dynamics: important implications for the calculation of event-related band power

Measures of event-related band power such as event-related desynchronization (ERD) are conventionally analyzed within fixed frequency bands, although it is known that EEG frequency varies as a function of a variety of factors. The question of how to determine these frequency bands for ERD analyses is discussed and a new method is proposed. The rationale of this new method is to adjust the frequency bands to the individual alpha frequency (IAF) for each subject and to determine the bandwidth for the alpha and theta bands as a percentage of IAF. As an example, if IAF equals 12 Hz, the widths of the alpha and theta bands are larger as compared to a subject with an IAF of, e.g., only 8 Hz. The results of an oddball paradigm show that the proposed method is superior to methods that are based on fixed frequencies and fixed bandwidths. Received: 22 July 1997 / Accepted in revised form: 22 April 1998     

The effects of various mental tasks on appearance of frontal midline theta activity in EEG.

A distinct theta rhythm of EEG in the frontal midline area during performance of mental tasks has been called Fm theta. One of the characteristics of Fm theta is individual differences in its appearance. The effects of various mental tasks and its repetition on appearance of Fm theta were investigated. Adding, correcting wrong words, short-term memory (STM) and counting cubes were imposed 6 times on 7 male students who didn't generate Fm theta at the previous experiment. Counting cubes evoked more Fm theta than the other three mental tasks. In every task the first trial showed little Fm theta, and the appearance time of Fm theta was enhanced by repetition. Type I of Spielberger's State-Trait Anxiety Inventory (STAI-I) demonstrated a higher state anxiety level of the subjects at the first trial. It may be concluded that the amount of Fm theta corresponds to the level in concentration of attention.     

Simultaneous biofeedback of heart rate and frontal EMG as a pretraining for the control of EEG theta activity

Following one base-line session, 20 normal subjects received four half hour sessions consisting of simultaneous feedback of heart rate and frontalis muscle (pretraining). Ten subjects received contingent (CF), the other ten noncontingent feedback (NCF). Subjects were asked to lower heart rate and frontal muscle tension (EMG). Heart rate within sessions decreased up to 19 bpm, with a mean of 4 bpm for the CF group. There was only a weak decrease over sessions, however, because of the strong habituation effect. The following events accompanied the heart rate decrease: (1) an increase of the variability of the heart rate, (2) a decrease of the variance of the EMG, (3) an increased correlation between heart rate slowing and EMG decrease, and (4) an increasing subjective experience of control of heart rate and EMG. After pretraining, subjects received eight sessions of auditory feedback of their frontal EEG theta activity (four sessions with CF and four sessions with NCF in balanced order). There was a weak increase of theta for the CF condition over sessions, but a decrease within the sessions. Pretraining on heart rate and frontal EMG control had no influence on the performance during theta training. It was hypothesized that control of heart rate slowing and theta control involve different mechanisms.     

Individual differences and variability in the timing of motor activity during walking in insects

The uniformity of the neural physiology of an animal population is a fundamental, rarely tested assumption in most neurophysiological work. In this study, the variability of the timing between the movements of pairs of legs during free walking in cockroaches was assessed. Phases (a measure of timing) of motor bursts in muscles of legs in the American cockroach, Periplaneta americana, were calculated for insects walking straight over a flat, level surface. Student's t, Wallraff, Mann Whitney and Watson U² two-sample tests were used to compare the phases of motor bursts of the same pairs of legs in different insects. The comparisons showed that in spite of the homogeneity both of the animal population and of the conditions under which the insects walked, most of the inter-leg phases of the animals that were compared were significantly different statistically. Further testing of greater numbers of insects using analysis of variance to test for population uniformity confirmed that the insects we tested were not members of a single statistical population with respect to the timing of motor bursts of the legs during walking. We infer that this unexpectedly large variability in a population thought to be relatively homogeneous reflects subtle but biologically significant differences between animals. The possible sources of these differences and their consequences for the study of behavior and its physiological basis are discussed.     

The differences in brain activity between narrow band noise and pure tone tinnitus

Background

Tinnitus is an auditory sensation characterized by the perception of sound or noise in the absence of any external sound source. Based on neurobiological research, it is generally accepted that most forms of tinnitus are attributable to maladaptive plasticity due to damage to auditory system. Changes have been observed in auditory structures such as the inferior colliculus, the thalamus and the auditory cortex as well as in non-auditory brain areas. However, the observed changes show great variability, hence lacking a conclusive picture. One of the reasons might be the selection of inhomogeneous groups in data analysis.

Methodology

The aim of the present study was to delineate the differences between the neural networks involved in narrow band noise and pure tone tinnitus conducting LORETA based source analysis of resting state EEG.

Conclusions

Results demonstrated that narrow band noise tinnitus patients differ from pure tone tinnitus patients in the lateral frontopolar (BA 10), PCC and the parahippocampal area for delta, beta and gamma frequency bands, respectively. The parahippocampal-PCC current density differences might be load dependent, as noise-like tinnitus constitutes multiple frequencies in contrast to pure tone tinnitus. The lateral frontopolar differences might be related to pitch specific memory retrieval.     

Individual differences in play inMacaca fuscata: The role of maternal status and proximity

Dominant and subordinate Japanese macaque (Macaca fuscata)females displayed differential treatment of offspring with respect to play. Offspring of more dominant females were more often observed in play than the offspring of a lowranking female. The levels of play in all juveniles varied as a function of the distance from the mother; play was more likely to occur at distances of greater than 3 m from the mother than at closer distances. Unlike the dominant females, the subordinate female maintained excessive contact with and proximity to her offspring. Mothers determined the complexity of the social environment in which their offspring matured by influencing the extent and nature of the peer play experiences of their offspring. This report is based on part of a master’s thesis submitted in partial fulfillment of the requirements for Master’s of Arts in Animal Behavior.     

Individual differences in the perception of probability

In recent studies of humans estimating non-stationary probabilities, estimates appear to be unbiased on average, across the full range of probability values to be estimated. This finding is surprising given that experiments measuring probability estimation in other contexts have often identified conservatism: individuals tend to overestimate low probability events and underestimate high probability events. In other contexts, repulsive biases have also been documented, with individuals producing judgments that tend toward extreme values instead. Using extensive data from a probability estimation task that produces unbiased performance on average, we find substantial biases at the individual level; we document the coexistence of both conservative and repulsive biases in the same experimental context. Individual biases persist despite extensive experience with the task, and are also correlated with other behavioral differences, such as individual variation in response speed and adjustment rates. We conclude that the rich computational demands of our task give rise to a variety of behavioral patterns, and that the apparent unbiasedness of the pooled data is an artifact of the aggregation of heterogeneous biases.     

Synchronized oscillations at alpha and theta frequencies in the lateral geniculate nucleus

In relaxed wakefulness, the EEG exhibits robust rhythms in the alpha band (8-13 Hz), which decelerate to theta (approximately 2-7 Hz) frequencies during early sleep. In animal models, these rhythms occur coherently with synchronized activity in the thalamus. However, the mechanisms of this thalamic activity are unknown. Here we show that, in slices of the lateral geniculate nucleus maintained in vitro, activation of the metabotropic glutamate receptor (mGluR) mGluR1a induces synchronized oscillations at alpha and theta frequencies that share similarities with thalamic alpha and theta rhythms recorded in vivo. These in vitro oscillations are driven by an unusual form of burst firing that is present in a subset of thalamocortical neurons and are synchronized by gap junctions. We propose that mGluR1a-induced oscillations are a potential mechanism whereby the thalamus promotes EEG alpha and theta rhythms in the intact brain.     

Functional aspects of evoked alpha and theta responses in humans and cats

A systems theoretical approach was used to compare possible functional roles of theta (4--7 Hz) and alpha (8--15 Hz) response components of brain evoked potentials. These response components were described earlier by Ba\c sar (1980). We recorded EEG and evoked potentials (EPs) from occipital scalp locations in 11 subjects. We used auditory and visual stimuli as inadequate and adequate stimuli, respectively (``cross-modality' measurements). The combined EEG-EP epochs were analysed in frequency domain with fast Fourier transform and adaptive digital filters. Alpha (8--15 Hz) response components turned out to be dependent on whether the stimulus was adequate or not (median amplitude with inadequate vs. adequate stimulation: vs. ). Theta (4--7 Hz) response components were less dependent on stimulus modality (inadequate vs. adequate stimulation: vs. ). In EP recordings the occipital alpha response almost disappeared in the first 250 ms following auditory stimulation. Comparable behaviour was observed in similar experiments with recordings from the cat visual cortex (area 17) and with occipital magnetoencephalographic recordings. Taking into account the above-mentioned previous reports on intracranial recordings in primary sensory areas of the cat brain and preliminary results of magnetoencephalographic measurements, we propose the following hypothesis: alpha responses in a time window of about 250 ms after stimulation might predominantly reflect primary sensory processing whereas the theta responses in the first 250 ms after stimulation might be more involved in supra-modality -- or cross-modality -- associative-cognitive processing. Received: 25 February 1994 / Accepted in revised form: 5 August 1994