Co-Planar Stereotaxic Atlas of the Human Brain—3-Dimensional Proportional System: An Approach to Cerebral Imaging, J. Talairach, P. Tournoux. Georg Thieme Verlag, New York (1988), 122 pp., 130 figs. DM 268

A voxel-based morphometric study of ageing in 465 normal adult human brains.

A pesar de la relativamente corta historia de la Psicologia como ciencia, existen pocos constructos psicologicos que perduren 90 anos despues de su formulacion y que, aun mas, continuen plenamente vigentes en la actualidad. El factor «g» es sin duda alguna uno de esos escasos ejemplos y para contrastar su vigencia actual tan solo hace falta comprobar su lugar de preeminencia en los modelos factoriales de la inteligencia mas aceptados en la actualidad, bien como un factor de tercer orden en los modelos jerarquicos o bien identificado con un factor de segundo orden en el modelo del recientemente desaparecido R.B.Cattell.

The g Factor: The Science of Mental Ability

A model of the effects of aging on brain activity during cognitive performance is introduced. The model is called HAROLD (hemispheric asymmetry reduction in older adults), and it states that, under similar circumstances, prefrontal activity during cognitive performances tends to be less lateralized in older adults than in younger adults. The model is supported by functional neuroimaging and other evidence in the domains of episodic memory, semantic memory, working memory, perception, and inhibitory control. Age-related hemispheric asymmetry reductions may have a compensatory function or they may reflect a dedifferentiation process. They may have a cognitive or neural origin, and they may reflect regional or network mechanisms. The HAROLD model is a cognitive neuroscience model that integrates ideas and findings from psychology and neuroscience of aging.

Hemispheric asymmetry reduction in older adults: the HAROLD model.

As we grow older, we may grow wiser, but we can also experience memory loss and cognitive slowing that can interfere with our daily routines. The cognitive neuroscience of human ageing, which relies largely on neuroimaging techniques, relates these cognitive changes to their neural substrates, including structural and functional changes in the prefrontal cortex, medial temporal lobe regions and white matter tracts. Much remains unknown about how normal ageing affects the neural basis of cognition, but recent research on individual differences in the trajectory of ageing effects is helping to distinguish normal from pathological origins of age-related cognitive changes.

/pdf/insights-into-the-ageing-mind-a-view-from-cognitive-z67u2m8evb.pdf

Insights into the ageing mind: a view from cognitive neuroscience.

The authors reviewed the evidence of age differences in episodic memory for content of a message and the context associated with it. Specifically, the authors tested a hypothesis that memory for context is more vulnerable to aging than memory for content. In addition, the authors inquired whether effort at encoding and retrieval and type of stimulus material moderate the magnitude of age differences in both memory domains. The results of the meta-analysis of 46 studies confirmed the main hypothesis: Age differences in context memory are reliably greater than those in memory for content. Tasks that required greater effort during retrieval yielded larger age differences in content but not in context memory. The greatest magnitude of age differences in context memory was observed for those contextual features that were more likely to have been encoded independently from content. Possible mechanisms that may underlie age differences in context memory-attentional deficit, reduced working memory capacity, and failure of inhibitory processing are discussed.

Differential effects of aging on memory for content and context: a meta-analysis.

Article abstract—We examined the pattern of neuroanatomic abnormalities in adults with Down9s syndrome (DS) and the cognitive correlates of these abnormalities. Specifically, we compared this pattern with what would be predicted by the hypotheses attributing DS pathology to either premature aging or Alzheimer9s disease. We measured a number of brain regions on MRIs of 25 subjects: 13 persons with the DS phenotype and 12 age- and sex-matched healthy volunteers. Study participants had no history of cardiovascular disease, diabetes, thyroid dysfunction, or seizure disorder. After statistical adjustment for differences in body size, we found that, in comparison with controls, DS subjects had substantially smaller cerebral and cerebellar hemispheres, ventral pons, mammillary bodies, and hip-pocampal formations. In the cerebellar vermis of DS subjects, we observed smaller lobules VI to VIII without appreciable differences in other regions. In addition, we noted trends for shrinkage of the dorsolateral prefrontal cortex, anterior cingulate gyrus, inferior temporal and parietal cortices, parietal white matter, and pericalcarine cortex in DS subjects compared with normal controls. The parahippocampal gyrus was larger in DS subjects. We found no significant group differences in the volumes of the prefiontal white matter, the orbitofiontal cortex, the pre- and postcentral gyri, or the basal ganglia. We conclude that the pattern of selective cerebral damage in DS does not clearly fit the predictions of the premature aging or Alzheimer9s disease hypotheses. To examine the relationship between brain abnormalities and cognitive deficits observed in DS, we correlated the size of brain regions that were significantly reduced in DS with performance on tests of intelligence and language. The correlational analysis suggested age-related decline in the DS subjects in general intelligence and basic linguistic skills. General intelligence and mastery of linguistic concepts correlated negatively with the volume of the parahippocampal gyrus. There was no relationship between total brain size and the cognitive variables.

Selective neuroanatomic abnormalities in Down's syndrome and their cognitive correlates: evidence from MRI morphometry.

Age-related differences in memory for facts, source, and contextual details were examined in healthy young (18-35 years old) and old (65-80 years old) volunteers. In all tested memory functions, decline over time was greater in the elderly than in the young. A time-dependent increase in the prevalence of source amnesia errors was clearly associated with old age. Contrary to several recent reports, measures of frontal lobe functions did not predict source memory. Nevertheless, some of these putative frontal function measures were related to memory for contextual details. The number of perseverative responses on the Wisconsin Card Sorting Test was inversely related to performance on both factual and contextual memory tests, but the association with contextual memory was stronger. Difficulties with response selection on a Stroop task predicted poor contextual memory in young but not in old adults.

Memory for facts, source, and context: Can frontal lobe dysfunction explain age-related differences?

• We investigated age-related differences in the cerebellar vermis. The areas of five vermal regions of interest were estimated from digitized midsagittal magnetic resonance imaging scans of 29 healthy volunteers and 30 neurologically intact patients (aged 18 to 78 years) who were free of vestibular symptoms, seizures, psychosis, or alcoholism. The five regions of interest included the following: (1) lingula and centralis, (2) culmen, (3) declive, folium, and tuber, (4) pyramis, and (5) uvula and nodulus. The ventral pons was used as a control region. After covarying skull size, we found a significant age-related reduction in the total area of the cerebellar vermis. The area of the dorsal regions declined with age, whereas the ventral segments of the vermis—lingula-centralis and uvula-nodulus—showed no significant age-related shrinkage. Notably, the area of the most dorsomedial portion, the declive-folium-tuber, tended to be more strongly associated with age than other segments. The pontine area was unaffected by age. No sex differences were found in the area of the vermis or its subdivisions, but the ventral pontine area was larger in male subjects than in female subjects, even after adjustment for skull size. The mechanisms underlying the observed differences are unclear. It appears, however, that phylogenetically more recent vermal regions, which are late to mature and are endowed with more extensive cortical connections, are the most vulnerable to the effects of aging.

Wesley D. Spencer

Papers

Differential effects of aging on memory for content and context: a meta-analysis.

Selective neuroanatomic abnormalities in Down's syndrome and their cognitive correlates: evidence from MRI morphometry.

Memory for facts, source, and context: Can frontal lobe dysfunction explain age-related differences?

Age-related regional differences in cerebellar vermis observed in vivo.

Neuroanatomical correlates of age-sensitive and age-invariant cognitive abilities: An in vivo MRI investigation