Jose F. Laguna

Fear recognition deficits after focal brain damage A cautionary note

Objective: To test the hypothesis that fear recognition deficits in neurologic patients reflect damage to an emotion-specific neural network. Background: Previous studies have suggested that the perception of fear in facial expressions is mediated by a specialized neural system that includes the amygdala and certain posterior right-hemisphere cortical regions. However, the neuropsychological findings in patients with amygdala damage are inconclusive, and the contribution of distinct cortical regions to fear perception has only been examined in one study. Methods: We studied the recognition of six basic facial expressions by asking subjects to match these emotions with the appropriate verbal labels. Results: Both normal control subjects (n = 80) and patients with focal brain damage (n = 63) performed significantly worse in recognizing fear than in recognizing any other facial emotion, with errors consisting primarily of mistaking fear for surprise. Although patients were impaired relative to control subjects in recognizing fear, we could not obtain convincing evidence that left, right, or bilateral lesions were associated with disproportionate impairments of fear perception once we adjusted for differences in overall recognition performance for the other five facial emotion categories. The proposed special role of the amygdala and posterior right-hemisphere cortical regions in fear perception was also not supported. Conclusions: Fear recognition deficits in neurologic patients may be attributable to task difficulty factors rather than damage to putative neural systems dedicated to fear perception.

A prospective study of physical trauma and multiple sclerosis.

During an eight year period 170 multiple sclerosis (MS) patients and 134 controls without physical impairment were followed closely to record all episodes of physical trauma and to measure their effect on exacerbation rate and progression of MS. There was a total of 1407 instances of trauma, which were sorted into various categories. Overall there was no significant correlation between all-traumas and disease activity. There was, however, a statistically significant negative correlation between traumatic episodes and exacerbations in 95 patients who had exacerbations during the programme, due primarily to less activity of the disease during a three month period following surgical procedures and fractures. Electrical injury had a significant positive association with exacerbation using a three month at-risk period, but there were no other significant positive correlations in any other category of trauma, including minor head injuries; there were no cases of head injury with prolonged unconsciousness. There was no linkage between the frequency of trauma and progression of disability. MS patients had two to three times more trauma than controls.

Uveitis, perivenous sheathing and multiple sclerosis.

Pars planitis (peripheral uveitis) and perivenous sheathing are two ocular phenomena associated with multiple sclerosis (MS). A total of 163 ocular examinations were performed on 127 MS patients at the university of Arizona Health Sciences Center. The prevalence of pars planitis in our study is lower (2.4 percent) than found by others, but significantly higher than its occurrence in the general population. We attribute our lower prevalence to the method of ocular examination (scleral depression and indirect ophthalmoscopy), as well as to firmly defined criteria necessary to make the diagnosis of pars planitis. The incidence of perivenous sheathing (11 percent) reported by us is consistent with the experience of others; however, this finding was noted more frequently in patients with the progressive form of MS. No perivenous sheathing was found to develop within the first few weeks following 31 exacerbations, and no association was identified between its presence and the severity of neurologic disability.

Face memory impairments in patients with frontal lobe damage

Objective: To determine whether damage to prefrontal cortex is associated with face memory impairment. Background: Neurophysiologic and functional imaging studies suggest that prefrontal cortex is a key component of a distributed neural network that mediates face recognition memory. However, there have been few attempts to examine the impact of frontal lobe damage on face memory performance. Methods:Patients with focal frontal lobe lesions and normal control subjects were administered two-alternative forced-choice and single-probe “yes/no” tests of recognition memory for novel faces. Retrograde memory was assessed by using famous faces as stimuli. Results: Compared with control subjects, patients with frontal lobe lesions showed evidence of marked anterograde and relatively mild retrograde face memory impairment. In addition, patients with right frontal lesions demonstrated increased susceptibility to false recognition, consistent with the breakdown of strategic memory retrieval, monitoring, and decision functions. Conclusions: Prefrontal cortex plays an important role in the executive control of face memory encoding and retrieval. Left and right prefrontal regions seem to make different contributions to recognition memory performance.

Priming effects in a letter-by-letter reader depend upon access to the word form system

Several types of cognitive and neuropsychological evidence suggest that priming effects on such implicit memory tests as word identification are mediated by a pre-semantic visual word form system that can operate independently of episodic memory. We investigate priming in a letter-by-letter reader, P.T., whose pattern of performance on neuropsychological tests indicates preservation of the word form system. Experiment 1 revealed robust priming on a word identification test following letter-by-letter study of target words, despite P.T.s great difficulty in identifying non-studied words. Experiment 2 showed that the priming effect was modality specific whereas Experiment 3 indicated that recall of previously studied words was not modality specific, thus indicating that the observed priming could not be attributed to explicit memory strategies. Experiment 4 revealed no priming of illegal nonwords on a letter identification test. The results support the notion that priming on the word identification test depends on access to the word form system.

Trauma as an etiologic and aggravating factor in multiple sclerosis

We carried out a retrospective and prospective epidemiologic study designed to detect an association between trauma and multiple sclerosis in 130 patients and 82 age- and sex-matched controls. Electrical injury was followed by an increased frequency of exacerbation, which did not achieve statistical significance. There was no statistically significant association between other types of trauma and onset or deterioration of the disease. These findings do not prove that such an association cannot exist for any one individual patient; however, they do not provide evidence to support this idea.

Endocrine factors influencing radiation injury to central nervous tissue

Abstract Corticosteroids have been shown experimentally to lower the tolerance of various normal tissues (lung, kidney, intestine) to irradiation. Pre-existing hypertension also modifies the effect of irradiation on the rat spinal cord and brain. Hypercorticism and hypertension co-exist in patients with Cushings disease. Although these patients are often approached therapeutically by irradiation, no reports concerning differences in the radiation sensitivity of nervous tissue between normal subjects (non-functioning pituitary adenomas) and those with hormonal imbalance and/or hypertension appear to be available. A comprehensive review of the literature revealed 14 patients with radiation damage to brain or to optic pathways following moderate doses for pituitary adenomas. Seven of the 14 patients (50%) had Cushings disease. This apparent higher incidence of radiation injury is significant if we consider that less than 5% of all patients receiving irradiation for pituitary adenomas have Cushings disease.

Diagnosis of carotid artery stenosis: comparison of oculoplethysmography and Doppler supraorbital examination.

Both Doppler supraorbital examination (OSM) and oculoplethysmography (OPG) were administered to 101 patients (202 arteries) to document the presence or absence of hemodynamically significant lesions of the internal carotid artery prior to angiography. There was no significant difference between the OSM and OPG with respect to diagnostic sensitivity or specificity, incidence of false-negative or false-positive results, and overall diagnostic accuracy. The diagnostic accuracy for the OSM and the OPG were 94.2% and 91.6%, respectively. In 171/202 (84.6%) arteries, the OSM and OPG were in diagnostic agreement, and the overall diagnostic accuracy of the combined tests was 97%. However, when the OSM and OPG did not agree (31/202 arteries, 15.4%), the diagnostic accuracy of neither the OSM nor the OPG was acceptable. Although the best diagnostic accuracy was obtained using two means of noninvasive cerebrovascular testing, in those instances where only one test may be available, the OPG would appear to be the test of choice. In those laboratories in which high diagnostic accuracy is obtained with the OSM, the addition of OPG testing will increase the overall diagnostic accuracy to a very high level. The presence of a midcervical bruit was found to have a very poor correlation with the incidence of hemodynamically significant stenoses of the internal carotid artery. Although both the OSM and OPG have minimal value in patients with symptomatic cerebrovascular disease, these tests play a very important role in screening patients for asymptomatic carotid stenosis or atypical cerebrovascular symptoms.

Confusion, dysphasia, and asterixis following metrizamide myelography.

A patient exhibited confusion, dysphasia, and striking asterixis 18 hours after metrizamide myelography. The symptoms lasted for a day and a half. While metrizamide is a useful contrast medium, side effects are not unusual and can, on occasion, be quite severe.

The modification of experimental allergic encephalomyelitis with epsilon aminocaproic acid

Epsilon aminocaproic acid, an inhibitor of plasminogen and trypsinogen activators, can decrease the severity of experimental allergic encephalomyelitis (EAE) in rats. The drug was tried because of a number of observations suggesting that neutral proteases, such as plasmin, might be chemical mediators of demyelination. The highest concentrations of plasminogen activator are found in the walls of veins and venules, around which demyelination is common in many demyelinating diseases, including MS. Indeed, the earliest lesion in MS is often demyelination with little cellular infiltration. In vitro studies have shown that neutral proteases secreted by activated macrophages selectively lyse myelin basic protein.