Dataset Information

Verbal and General IQ Associate with Supragranular Layer Thickness and Cell Properties of the Left Temporal Cortex.

ABSTRACT: The left temporal lobe is an integral part of the language system and its cortical structure and function associate with general intelligence. However, whether cortical laminar architecture and cellular properties of this brain area relate to verbal intelligence is unknown. Here, we addressed this using histological analysis and cellular recordings of neurosurgically resected temporal cortex in combination with presurgical IQ scores. We find that subjects with higher general and verbal IQ scores have thicker left (but not right) temporal cortex (Brodmann area 21, BA21). The increased thickness is due to the selective increase in layers 2 and 3 thickness, accompanied by lower neuron densities, and larger dendrites and cell body size of pyramidal neurons in these layers. Furthermore, these neurons sustain faster action potential kinetics, which improves information processing. Our results indicate that verbal mental ability associates with selective adaptations of supragranular layers and their cellular micro-architecture and function in left, but not right temporal cortex.

SUBMITTER: Heyer DB

PROVIDER: S-EPMC9157308 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Verbal and General IQ Associate with Supragranular Layer Thickness and Cell Properties of the Left Temporal Cortex.

Heyer D B DB Wilbers R R Galakhova A A AA Hartsema E E Braak S S Hunt S S Verhoog M B MB Muijtjens M L ML Mertens E J EJ Idema S S Baayen J C JC de Witt Hamer P P Klein M M McGraw M M Lein E S ES de Kock C P J CPJ Mansvelder H D HD Goriounova N A NA

Cerebral cortex (New York, N.Y. : 1991) 20220501 11

The left temporal lobe is an integral part of the language system and its cortical structure and function associate with general intelligence. However, whether cortical laminar architecture and cellular properties of this brain area relate to verbal intelligence is unknown. Here, we addressed this using histological analysis and cellular recordings of neurosurgically resected temporal cortex in combination with presurgical IQ scores. We find that subjects with higher general and verbal IQ scores ...[more]

PMID: 34550325

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Project description:BackgroundTreating memory and cognitive deficits requires knowledge about anatomical sites and neural activities to be targeted with particular therapies. Emerging technologies for local brain stimulation offer attractive therapeutic options but need to be applied to target specific neural activities, at distinct times, and in specific brain regions that are critical for memory formation.MethodsThe areas that are critical for successful encoding of verbal memory as well as the underlying neural activities were determined directly in the human brain with intracranial electrophysiological recordings in epilepsy patients. We recorded a broad range of spectral activities across the cortex of 135 patients as they memorised word lists for subsequent free recall.FindingsThe greatest differences in the spectral power between encoding subsequently recalled and forgotten words were found in low theta frequency (3-5 Hz) activities of the left anterior prefrontal cortex. This subsequent memory effect was proportionally greater in the lower frequency bands and in the more anterior cortical regions. We found the peak of this memory signal in a distinct part of the prefrontal cortex at the junction between the Broca's area and the frontal pole. The memory effect in this confined area was significantly higher (Tukey-Kramer test, p<0.05) than in other anatomically distinct areas.InterpretationOur results suggest a focal hotspot of human verbal memory encoding located in the higher-order processing region of the prefrontal cortex, which presents a prospective target for modulating cognitive functions in the human patients. The memory effect provides an electrophysiological biomarker of low frequency neural activities, at distinct times of memory encoding, and in one hotspot location in the human brain.FundingOpen-access datasets were originally collected as part of a BRAIN Initiative project called Restoring Active Memory (RAM) funded by the Defence Advanced Research Project Agency (DARPA). CT, ML, MTK and this research were supported from the First Team grant of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund.

Project description:ObjectiveLeft hippocampal sclerosis (HS) is associated with verbal-specific memory impairment. This association is well established for word list learning tasks, and there is some evidence that this may also be relevant to verbal paired associates learning (PAL), though the evidence is limited. We aimed to evaluate the utility of verbal PAL as a marker for left HS, compare this with word list learning, and derive cutoff scores to facilitate clinical application.MethodsRetrospective analysis of Rey Auditory Verbal Learning Test (RAVLT) and PAL scores obtained from 116 surgically naïve temporal lobe epilepsy patients with HS (14 bilateral, 57 left, 45 right; range of N across test indices: 77-110).ResultsRelative to right HS, left HS and bilateral HS were associated with poorer performance on PAL Hard Pairs (p < 0.001) and all RAVLT indices (p < 0.001), with performance comparable in left HS and bilateral HS (p > 0.05). PAL Hard Pairs and all RAVLT indices displayed acceptable discriminatory ability (AUC > 0.70) in classifying left-sided HS (unilateral left or bilateral HS), with RAVLT delayed recall the strongest predictor (AUC = 0.87; PAL Hard Pairs Learning and Delay = 0.80 and 0.83, respectively). Optimal cutoff scores for left-sided HS classification were generated.SignificanceAlthough the RAVLT delayed recall was the strongest predictor of left-sided HS, PAL Hard Pairs also demonstrated excellent discriminatory capacity, offering an additional cognitive marker of left hippocampal integrity to complement word list learning in clinical assessments.Plain language statementThe results of the study show that the ability to learn unrelated pairs of words (e.g., "silver"-"run") is compromised in the setting of epilepsy with left-sided hippocampal sclerosis (HS), be it unilateral left HS or bilateral HS. The ability of unrelated word pair learning to discriminate left vs. right HS was comparable to word list learning, a task with demonstrated sensitivity to left HS. Our results suggest that the ability to learn unrelated pairs of words provides another useful marker of left-sided hippocampal compromise in epilepsy. We provide cutoff scores to facilitate clinical interpretation.

Dataset Information

Verbal and General IQ Associate with Supragranular Layer Thickness and Cell Properties of the Left Temporal Cortex.

Publications

Verbal and General IQ Associate with Supragranular Layer Thickness and Cell Properties of the Left Temporal Cortex.

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