PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 7670761

The hippocampus: functional and structural correlations.

S A Baxendale
View original source ↗Export metadata ↓

Abstract

This paper reviews the current literature relating neuropsychological measures of the functional integrity of the hippocampus with structural indices obtained from magnetic resonance imaging (MRI) volumetric scans and the histological analysis of postoperative specimens. The first part of the discussion presents an overview of the current methods and applications of volumetric MRI of the hippocampus. The processes and contemporary standards applied to the histological analysis of resected hippocampal tissue are also described. Both of these measures of structural integrity have been studied in relation to preoperative performance on neuropsychological tests, including the intracarotid sodium amytal test, and postoperative memory functioning. The findings from these studies are reviewed. The challenges presented by these new technologies to the field of neuropsychology are discussed.

Explore related subjects

Brain MappingEpilepsy, Temporal LobeHippocampusHumansMagnetic Resonance ImagingMental RecallNeuropsychological TestsPostoperative ComplicationsPsychosurgeryRetention, PsychologySclerosisJournal ArticleReview

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

S A Baxendale. 1995. The hippocampus: functional and structural correlations.. https://doi.org/10.1016/s1059-1311(95)80089-1

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2001

Evoked and oscillatory neuromagnetic responses to sniffing odor in human subjects.

We studied neuromagnetic responses to sniffing air and odor of lemon, lavender or soy sauce in two human subjects. Simple averaging of the data with respect to the onsets of the sniffs yielded odor-specific evoked responses over the right cortex with peak latency about 350 ms after the onsets. When the data were passed through band-pass filters centered around 48 Hz and of 320 ms in duration, rectified and then averaged, they yielded peaks, indicating transient oscillations, over the right frontal cortex with longer latency. We found such peaks in only 9 out of 26 experiments of sniffing odor, however.

Brain Mapping↗
PubMed2001

Cortical localization of reading in normal children: an fMRI language study.

BACKGROUND: fMRI provides a noninvasive means of identifying the location and organization of neural networks that underlie cognitive functions. OBJECTIVE: To identify, using fMRI, brain regions involved in processing written text in children. METHODS: The authors studied nine normal right-handed native English-speaking children, aged 10.2 years (range 7.9 to 13.3 years), with two paradigms: reading Aesop's Fables and "Read Response Naming" (reading a description of an object that was then silently named). Data were acquired using blood oxygen level-dependent fMRI. Group data were analyzed with statistical parametric mapping; individual data sets were analyzed with a region-of-interest approach from individual study t maps. The number of activated pixels was determined in brain regions and an asymmetry index (AI = [L - R]/[L + R]) calculated for each region. RESULTS: The authors found strong activation in the left middle temporal gyrus and left midfrontal gyrus and variable activation in left inferior frontal gyrus for both reading tasks in the group analysis (z > 5.5 to 9.1). All subjects had strong left-sided lateralization for both tasks in middle/superior temporal gyrus, inferior frontal gyrus, and middle frontal gyrus (AI = 0.76 to 1.0 for t = 4). Reading Fables activated twice as many pixels in temporal cortex as the Read Response Naming task; activation in dorsolateral prefrontal cortex was similar for both tasks. Small homologous right middle temporal region activation was seen with reading a fable. CONCLUSIONS: The neural networks that process reading appear to be lateralized and localized by middle to late childhood. Reading text paradigms may prove useful for identifying frontal and temporal language-processing areas and for determining language dominance in children experiencing epilepsy or undergoing tumor surgery.

Brain Mapping↗
PubMed2001

Effects of motor imagery on motor cortical output topography in Parkinson's disease.

BACKGROUND: The motor impairment in Parkinson's disease (PD) could partly reflect a failure to activate processes of motor imagery. OBJECTIVE: To verify any selective changes of motor output during motor imagery, lateralized to the hemisphere contralateral to the clinically affected side of hemiparkinsonian patients. METHODS: Transcranial magnetic stimulation (TMS) was used to map the cortical representations of the contralateral abductor digiti minimi muscle (ADM) during rest, contraction, and motor imagery in a group of patients with hemi-PD and in a group of healthy volunteers. Seven patients with hemi-PD and seven healthy subjects were examined. Focal TMS was applied over a grid of 20 scalp positions on each hemiscalp. Maps were characterized by area (number of excitable positions), volume (the sum of motor evoked potential amplitudes at all scalp positions), and center of gravity (a map position representing an amplitude-weighted calculation of the excitable area). RESULTS: In healthy control subjects, the area of cortical representation of ADM was symmetrically increased in both hemispheres by mental simulation of movement and real muscle contraction. In patients with hemi-PD, there was a hemispheric asymmetry in the area of cortical representation elicited by motor imagery. The area was reduced in the clinically affected hemisphere. The volume of cortical representation was increased under all conditions and in both hemispheres in patients with PD. However, largely because the volume was so high at rest in patients, the increment in volume associated with contraction was smaller than in control subjects. CONCLUSION: This study demonstrates the presence of a tonic hyperactivation of motor cortical circuitry in PD in conjunction with an abnormality of either motor imagery or the process by which motor imagery engages the sensorimotor cortices in the clinically affected hemisphere.

Brain Mapping↗