Biomedical subjects

N Ehrlé

Publications and source records attributed to N Ehrlé.

5 recordsLinked to original sources

PubMed2001

Time estimation in patients with right or left medial-temporal lobe resection.

Patients with either left or right antero-medial-temporal lobe (MTL) resection were investigated as to their ability to reproduce and produce three durations (5, 14, or 38 s) in three conditions (silence, counting, articulatory suppression). The results showed that patients with unilateral MTL lesions did not differ from controls when they had to encode the duration of a visual stimulus in order to reproduce it. By contrast, patients with right MTL lesions underestimated all three durations, compared with controls and with patients with left MTL resection, when they had to produce durations given in chronometric units. This finding suggests that the right MTL retains long-term representations of the conventional units necessary to the accurate production of durations.

Adolescent↗

PubMed2001

Processing of rapid auditory information in epileptic patients with left temporal lobe damage.

The role of the temporal lobes in processing time-related (temporal) information was tested in a task of anisochrony (or irregularity) discrimination assessing the temporal processing of sequential auditory information according to different presentation rates or tempos (between 80 and 1000 ms inter-onset intervals, IOI). Epileptic patients with either left (LHA, n=8) or right (RHA, n=10) hippocampal atrophy participated in this study as well as six normal control subjects (NC). For all the subjects, an effect of tempo was obtained, thresholds deteriorating for the 80 ms IOI as compared to longer IOI (the latter conforming to Weber's law). Furthermore, there was a specific impairment of rapid anisochrony discrimination (80 ms IOI) for patients with LHA as compared to patients with a RHA and NC, whereas no significant deficit was observed in these patients for longer IOI. These findings are in agreement with studies carried out in patients with left-hemisphere damage associated with massive language disorders and suggest the specialisation of left medial temporal lobe structures in processing rapid sequential auditory information. However, these results might also be explained by an auditory memory deficit in the presence of left temporal lobe dysfunction, as opposed to a specific impairment of fast sequential temporal processing.

Adolescent↗

PubMed2001

Cerebral substrates for musical temporal processes.

Music as well as language consists of a succession of auditory events in time, which require elaborate temporal processing. Although several lines of evidence suggest that the left dominant hemisphere is predominantly involved in the processing of rapid temporal changes of speech, very little is known about the cerebral substrates underlying such auditory temporal processes in music. To investigate this issue, we examined epileptic patients with either left (LTL) or right (RTL) temporal lobe lesions as well as normal control subjects (NC) in two different tasks involving the processing of time-related (temporal) information. By manipulating the interonset interval (IOI) in a psychophysical task, as well as in a task of detection of rhythmic changes in real tunes, we studied the processing of temporal microvariations in music. The first task assessed anisochrony (or irregularity) discrimination of sequential information according to different presentation rates (between 80 and 1000 ms IOI). For all subjects, an effect of tempo was obtained; thresholds were lower for the 80 ms IOI than for longer IOIs. Furthermore, there was a specific impairment of rapid anisochronous discrimination (80 ms IOI) for LTL patients as compared to RTL and NC subjects, but no deficit was observed for longer IOIs. These findings suggest the specialization of left temporal lobe structures in processing rapid sequential auditory information. The second task involved the detection of IOI increments in familiar monodic tunes. Performance was measured for two increments (easy vs. difficult to detect according to cognitive expectation) to assess the effect of cognitive expectation using a forced-choice paradigm (changed vs. unchanged melody). The results showed that LTL patients but not RTL were impaired as compared to NC subjects in the increment detection. However, all groups showed differences between the two levels of difficulty, suggesting that top-down processing remains functional. These findings suggest that left temporal lobe structures are predominantly involved in perceiving time-related perturbations in familiar tunes as well as in isochronous sequences, extending to the musical domain findings previously reported in speech.

Auditory Perception↗

PubMed1999

Spatial memory deficits in patients with lesions affecting the medial temporal neocortex.

Lesion studies in monkeys suggest that neocortical subregions of the medial temporal lobe (MTL) carry memory functions independent of the hippocampal formation. The present study investigates possible differential contributions of MTL subregions to spatial memory in humans. Eye movements toward remembered spatial cues (memory-guided saccades) with unpredictably varied memorization delays of up to 30 seconds were recorded in patients with postsurgical lesions of the right MTL, either restricted to the hippocampal formation (n = 3) or including the adjacent neocortex (n = 5) and in 10 controls. Although saccadic targeting errors of patients with selective hippocampal lesions did not differ from controls, saccadic targeting errors of patients with additional neocortical involvement showed a significant and contralaterally pronounced increase at memorization delays above 20 seconds. We conclude that the human medial temporal neocortex carries spatial memory functions independent of the hippocampal formation and distinct from spatial short-term memory.

Adult↗

PubMed1999

Specificity of memory deficits after right or left temporal lobectomy.

An impairment of verbal memory has consistently been associated with resection of the left dominant temporal lobe, whereas non-verbal memory deficits have been less reliably observed following resection of the right temporal lobe. Such a dissociation may be due to material-specific differences of processing between verbal and non-verbal information. Alternatively, the influence of the left and right limbic structures may vary according to the stage of memory processing. The aim of the study was to test these hypotheses by comparing verbal and spatial learning in patients with left or right temporal lobe resection for intractable epilepsy, using verbal and visuospatial memory tasks with the same design: control of encoding, multiple trial learning, free and cued recall, short and long delays. The results showed: (1) a similar pattern of learning and recall in the two groups; (2) a higher performance in spatial learning for patients with left temporal lobe resection and in verbal learning for patients with right temporal lobe resection; (3) material-specific effects characterized by a higher sensitivity to cues in the verbal domain and a better retention of information during delays in the spatial domain. These results suggest parallel processing of the two temporal lobes at the various memory stages, rather than an interaction between memory stage and side of the lesion similar to that already proposed for the frontal lobes. They also confirm a double dissociation between verbal/spatial information processing and side of temporal lobe resection.

Adult↗