Prospective remembering in younger and older adults: role of the prospective cue.

In these studies, adult age differences in event-based prospective memory were examined using an adapted version of G.O. Einstein and M.A. McDaniel's (1990) task. In Experiments 1-3, we varied prospective cue specificity by assigning a specific target word or an unspecified word drawn from a given taxonomic category. In Experiment 3, we manipulated cue typicality by presenting low or high typicality target words. Results yielded positive effects of cue specificity on prospective performance. Age effects occurred when high typicality target words served as prospective cues (Exps. 1 and 3), but younger and older adults performed comparably with moderate and low typicality words (Exps. 2 and 3). Hierarchical regression analyses indicated that age accounted for a small but significant amount of variance in prospective memory, although the contribution of age was substantially reduced after statistically controlling for recognition memory. Implications of these data for current views on prospective remembering are discussed.

Quantitative PET findings in patients with posttraumatic anosmia.

OBJECTIVE: To investigate quantitative positron emission tomography (PET) findings, particularly from orbitofrontal cortex, in patients with posttraumatic anosmia. SETTING: Neuropsychology outpatient clinic and university brain imaging center. SUBJECTS: Eleven patients with head injury resulting in severe anosmia and 11 controls matched for age. All 11 head-injured patients had their head injuries at least 2 years before involvement in the study. MEASURES: Regional cerebral glucose metabolism was measured with PET. RESULTS: Quantitative evaluation of PET findings for anosmic patients as a group showed orbitofrontal hypometabolism compared with controls. Decreased activity was also noted in mesial temporal lobe. Activity in subcortical white matter was essentially identical between groups. CONCLUSIONS: Findings strongly suggest that posttraumatic anosmia is closely associated with hypometabolism in the orbitofrontal cortex and the medial prefrontal cortex. The results also underscore the importance of posttraumatic anosmia as a clinical sign of orbitofrontal damage, as has been shown previously with neuroSPECT (single photon emission computed tomography).

Stability of postconcussion symptomatology differs between high and low responders and by gender but not by mild head injury status.

A large sample of undergraduates (N = 2,326) were screened for general health. The screen discretely included items assessing postconcussion symptomatology and neurologic history. A subsample of experiment-blind participants whose self-reported postconcussion symptom levels were >0.5 SD below the screening sample mean (low symptomatic; n = 45) or >0.5 SD above the screening sample mean (high symptomatic; n = 53) were re-evaluated for postconcussion symptomatology 3 to 90 days later. The sample included 50 participants who reported history of mild head injury (MHI) and 48 controls. MHI was defined as loss of consciousness of < or =20 minutes within the past 10 years, but no more recent than 3 months. Persons with history of >1 head injury or with other neurologic history were not included in the study. The stability of postconcussion symptoms differed by high symptomatic versus low symptomatic presentation (high symptomatic presentation was more variable) and by gender (females were more variable), but not by actual history of MHI. Sex differences in self-reported postconcussion symptomatology are consistent with gender-related differences in reporting of other physical and psychological symptoms. In addition to demonstrating differences in the stability of self-reported postconcussion symptomatology, the current study provides normative test-retest data for the Postconcussion Symptom Checklist for extreme responders by gender and MHI status.

Quantitative PET scan findings in carbon monoxide poisoning: deficits seen in a matched pair.

Quantitative positron emission tomography (PET) was utilized to establish the degree and localization of central nervous system dysfunction in 2 adult patients 3 years status postchronic carbon monoxide poisoning. The individual PET scans were compared against a composite scan made up of 32 normals using a z transformation statistical parametric map. Neuropsychological findings indicated marked anterior frontal lobe syndrome in the context of far-above-average intelligence, memory, and language. They also showed manifest frontal symptoms in activities of daily living that resulted in vocational disability in each case. PET analysis revealed substantially decreased metabolism in the orbitofrontal and dorsolateral prefrontal cortex as well as in areas of the temporal lobe for each individual. Individual scans were very similar and consistent with patient's presenting symptoms, and changed life circumstances. This report represents the first quantitative functional neuroimaging study relevant to carbon monoxide poisoning.

PET scan findings in a patient with a remote history of exposure to organic solvents.

This is a single-case study employing positron emission tomography (PET) scanning and neuropsychological assessment on a 47-year-old male with a 15-year history of repeated respiratory and dermal exposure to high levels of organic solvents with at least 750 peak exposures (i.e., solvent "intoxication"). At age 43, he presented with neuropsychological symptoms of a solvent encephalopathy and multiple abnormalities in his peripheral neurological examination but had normal MRI and EEG findings. Four years after cessation of exposure to degreasing and solvent chemicals, the patient produced a grossly abnormal PET scan in which frontal, hippocampal, and parietal hypometabolism were particularly noteworthy. During this same 4-year period of nonexposure, modest improvements in neuropsychological testing were noted, along with substantial improvements in partial seizurelike symptoms. Frontal lobe deficits elicited in testing and from collateral interview, however, did not change. Findings suggest that repeated peak exposures to organic solvents m y result in a neurobehaviorally complex solvent syndrome caused by central nervous system damage that is readily apparent on PET scan, even though it is not evident in either imaging technologies. In addition, the case is the first reported in which functional neuroimaging was employed to study a patient with chronic solvent encephalopathy many years after cessation of solvent exposure.

Fine tuning the graphesthesia assessment: one stroke versus two.

The Finger-Tip Number-Writing test (Reitan, 1967; Reitan & Wolfson, 1993) is a standardized neuropsychological procedure for the evaluation of tactile perception. Test standardization has neglected to consider the variability associated with the way in which the numerals are traced. We present findings that suggest that the sensitivity of the test can be increased by tracing all numerals with one stroke.

Corpus callosum surface area across the human adult life span: effect of age and gender.

This magnetic resonance (MR) imaging study analyzed and provides normative data on the midsagittal surface area of the corpus callosum (CC) across the human adult life span in 200 normal volunteers. Using MR imaging scans, CC midsagittal surface area was quantified, along with midsagittal intracranial surface area and total intracranial volume (measures of cranial size). Results demonstrate that when head size is controlled, no major changes associated with normal aging are evident in the CC during the more active years of adult life span (up through 65). Overall, females had significantly larger CC relative to total intracranial volume. Results are discussed in terms of potential gender differences in CC size and the clinical application of this normative data.