The neurophysiological bases of high IQ

The developmental trajectory of functional excitation-inhibition balance relates to language abilities in autistic and allistic children

Autism is a neurodevelopmental condition that has been related to an overall imbalance between the brain's excitatory (E) and inhibitory (I) systems. Such an EI imbalance can lead to structural and functional cortical deviances and thus alter information processing in the brain, ultimately giving rise to autism traits. However, the developmental trajectory of EI imbalances across childhood and adolescence has not been investigated yet. Therefore, its relationship to autism traits is not well understood. In the present study, we determined a functional measure of the EI balance (f-EIB) from resting-state electrophysiological recordings for a final sample of 92 autistic children from 6 to 17 years of age and 100 allistic (i.e., non-autistic) children matched by age, sex, and nonverbal-IQ. We related the developmental trajectory of f-EIB to behavioral assessments of autism traits as well as language ability. Our results revealed differential EI trajectories for autistic compared to allistic children. Importantly, the developmental trajectory of f-EIB values related to individual language ability. In particular, elevated excitability in late childhood and early adolescence was linked to decreased listening comprehension. Our findings provide evidence against a general EI imbalance in autistic children when correcting for non-verbal IQ. Instead, we show that the developmental trajectory of EI balance shares variance with autism trait development at a specific age range. This is consistent with the proposal that the late development of inhibitory brain activity is a key substrate of autism traits.

Temporal regularity of cerebral activity at rest correlates with slowness of reaction times in intellectual disability

OBJECTIVE

Intellectual disability (ID) is described as a general slowness in behavior and an inadequacy in adaptive skills. The present study examines whether behavioral slowness in ID could originate from abnormal complexity in brain signals.

METHODS

Participants (N = 29) performed a reaction times (RTs) task assessing their individual information processing speeds. Half of the participants had moderate intellectual disability (intelligence quotient (IQ) < 70). Continuous electroencephalogram recording during the resting period was used to quantify brain signal complexity by approximate entropy estimation (ApEn).

RESULTS

For all participants, a negative correlation between RTs and IQ was found, with longer RTs coinciding with lower IQ. This behavioral slowness in ID was associated with increased temporal regularity in electrocortical brain signals.

CONCLUSIONS

Behavioral slowness in ID subjects is closely related to lower brain signal complexity.

SIGNIFICANCE

Brain signal ApEn is shown to correspond with processing speed for the first time: in ID participants, the higher the regularity in brain signals at rest, the slower RTs will be in the active state. ID should be understood as a lack of lability in the cortical transition to the active state, weakening the efficiency of adaptive behavior.

Sex, Temperament, and Language-Related Differences in Examination Performance: A Study of Multiple-Choice and Written-Answer Tests

Arousability theory of Robinson predicts sex differences in temperament and in verbal ability and cognitive processing. Related hypotheses were tested in a sample of 73 Kuwaiti 3rd-year medical students by analysis of data obtained from administration of the Eysenck Personality Questionnaire and from questions requiring written answers or multiple-choice answers in an examination in psychology. Principal components analysis yielded a large sex difference in word production and indicated that variance of written answers loaded on two uncorrelated “linguistic” and “knowledge/cognition” components. Sex differences in temperament were also manifest but these contributed little to the observed differences in examination performance. Statistical tests indicated no sex difference in multiple-choice performance, but the women produced more words than the men and did better on the written-answer questions. In addition, there were substantial and statistically significant correlations between word production and performance on both types of test. The results confirmed predictions from arousability theory that the multiple-choice questions provided a more equitable basis than short written answers for examining classes of men and women in medical school. Written answers for questions could penalise students who are shown to be less proficient in the use of English as a second language.

In pursuit of knowledge

This article is based on the proposition that to understand the nature of knowledge, and how best to acquire it, one must look first at how the brain abstracts knowledge from the information provided by sensory receptors. The nature of this biological process of knowledge acquisition is suggested by the necessary conditions for the occurrence of learning, and from consideration of these necessary conditions in terms of what is currently known about the properties and limitations of neural systems. This entails discussion of an important distinction that must be made between "perceptual" and "associative" learning and between the neural systems required to mediate these two kinds of learning. There is also discussion of the manner in which language can overcome the limitations of neurological systems to greatly extend the scope of associative learning. This leads on to discussion of the role of active efferent language systems and temporary memory in the mediation of thinking. Consideration of the main features of the biological process of knowledge acquisition confirms, and extends to perception, Hume's famous conclusion that knowledge derives from the similarity or temporal contiguity of recurring events. New insights are also obtained concerning the biological causes of bias in the knowledge acquisition process, concerning the intellectual process of theory generation, and concerning the role of theory in the conduct of empirical research. Finally, and most importantly, it can be concluded that all knowledge is theory and hence that the ultimate goal of science is the development of better theories.

Correlations between ERP parameters and intelligence: a reconsideration

The present study investigated differences in ERP parameters related to intelligence. For that purpose 74 individuals (Intelligence: M=107; S.D.=12; range 73-135), of average creativity passively listened to two tones and performed two auditory, and two visual oddball tasks while their EEG was recorded. The approximate entropy parameters, peak latencies and amplitudes were determined. The correlation coefficients indicated that in the attended conditions, the more intelligent individuals showed more regular ERP waveforms than less intelligent individuals. It was further found that less intelligent individuals showed increased P300 latencies and reduced amplitudes. The differences were explained with a more specific engagement of neural networks in more intelligent individuals.

The technical, neurological and psychological significance of 'alpha', 'delta' and 'theta' waves confounded in EEG evoked potentials: a study of peak latencies

It is suggested that lack of progress in understanding the neurological and psychological significance of EEG averaged evoked potentials (AEPs) and event related potentials (ERPs) may be due to the confounding of, 'delta', 'theta' and 'alpha' frequency responses generated by the 'brain-stem' 'limbic' and 'thalamic' cortical activating systems, respectively. This hypothesis was tested in a sample of 93 adults by recording EEG responses to auditory tones and using narrow-band filters to distinguish '4 Hz', '7 Hz', and '10 Hz' component waves in the unfiltered AEP. Bivariate and multivariate statistical analyses of peak latencies provided evidence of the distinct and unitary nature of these component waves and demonstrated their relative influence on the P1, N1 and P2 peaks of the unfiltered AEP. The results also reveal a predicted negative relationship between the 10 and 4 Hz latencies which is attributed to inhibition of the delta frequency brain-stem ascending reticular activating system (BSARAS) by the alpha frequency diffuse thalamic projection system (DTPS). Correlations of the 4 Hz latencies, with age, sex, and behavioural arousal variables confirm that the 4 Hz latencies are associated with the maintenance of behavioural arousal, an important function of the BSARAS.

Visual evoked potentials, attention and mnemonic abilities in children

We analyzed the correlation between attention and mnemonic processes and different visual evoked potential (VEP) parameters. A group of 34 children between 9 and 13 years old was studied. VEPs were recorded in C3, C4, P3, P4, O1, O2, T5 and T6 with linked ear lobes as reference. Two different types of stimuli were used: flash and checkerboard pattern. The power of VEPs was calculated as the sum of the square amplitude values for different time epochs. Correlation coefficients between left and right homologous VEPs were also computed. A visual selective attention task divided into 5 items of increasing difficulty and the Sternberg paradigm were applied. The performance was automatically evaluated by the computer, giving the number of correct responses (NCR) and other measures of performance. Correlation coefficients between VEP parameters and the scores obtained in the performance of tasks were calculated. It was observed that power in P3, P4, T5, and T6 and the correlation coefficients between central, parietal and temporal VEPs were positively correlated with NCR of both tasks. However, power in O1 and O2 was negatively correlated with NCR.