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Biomedical subjects

J F Laguna

Publications and source records attributed to J F Laguna.

At least 19 recordsLinked to original sources
PubMed2001

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.

Adult↗
PubMed2000

Hyper-reflexia without spasticity after unilateral infarct of the medullary pyramid.

Whether or not a lesion confined to the pyramidal tract produces spasticity in humans remains an unresolved controversy. We have studied a patient with an ischemic lesion of the right medullary pyramid, using objective measures of hyper-reflexia, spasticity, and weakness. Electromyographic activity (EMG) of the biceps muscles was recorded under the following conditions: (1) in response to a tendon tap with an instrumental reflex hammer, (2) in response to imposed quick stretch with motion analysis, and (3) during an isometric holding task. Hyper-reflexia of the involved arm in response to tendon tap was shown to be due primarily to an increase in the gain of the reflex arc. No velocity-dependent increase in the response to quick stretch of the involved arm was present. This was consistent with the absence of detectable spasticity on the clinical exam. These findings suggest that a lesion confined to the medullary pyramid can give rise to weakness and hyper-reflexia without causing spasticity. Moreover, these findings suggest that different anatomical substrates may underlie the clinical phenomena of hyper-reflexia and spasticity.

Aged↗
PubMed2000

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.

Adult↗
PubMed1991

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.

Adult↗
PubMed1990

From letters to words: procedures for word recognition in letter-by-letter reading.

There are two alternative interpretations of how word recognition is accomplished in letter-by-letter reading. One postulates that it relies on the spelling system operating "in reverse," whereas the other claims that it is mediated by the reading system. Because of the close association between patterns of reading and spelling in previously reported cases of letter-by-letter reading, both hypotheses may be considered equally plausible. We now report a patient with letter-by-letter reading who demonstrated a striking dissociation between reading and spelling. Our observations in this patient argue against the concept of "reading via spelling" and suggest that word recognition in letter-by-letter reading is mediated by the orthographic input lexicon used in normal reading.

Agraphia↗
PubMed1981

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.

Electric Injuries↗
PubMed1980

Aberrant regeneration in idiopathic oculomotor nerve palsy: case report.

Aberrant regeneration of the oculomotor nerve usually follows injury to the nerve by posterior communicating arty aneurysms or trauma. A case of idiopathic third nerve palsy with pupillary involvement occurred in an otherwise healthy 38-year-old man. Follow-up examination 32 months later showed evidence of oculomotor function with aberrant regeneration.

Adult↗
PubMed1979

Paraneoplastic vasculitis of nerve: a remote effect of cancer.

The development of mononeuritis multiplex brought three men to medical attention weeks to months prior to the diagnosis of a malignancy. In each case, sural nerve biopsy exhibited active wallerian degeneration with vasculitis. Two of the men died and at autopsy were found to have clinically unrecognized oat cell carcinoma and carcinomatous sensory neuropathy with brainstem encephalitis. The third patient is still alive but was found to have a lymphoma and has subsequently developed a liposarcoma. The vasculitis in all 3 cases seems limited mainly to the peripheral nervous system. Mononeuritis multiplex due to vasculitis may represent a new remote effect of cancer on the nervous system.

Brain Stem↗
PubMed1978

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.

Aminocaproates↗