PubMed Health⌕ Search

Biomedical subjects

N Georgieff

Publications and source records attributed to N Georgieff.

12 recordsLinked to original sources
PubMed2001

Abnormal peripheral auditory asymmetry in schizophrenia.

OBJECTIVE: Auditory processing difficulties have been reported in schizophrenia. This study explores peripheral auditory function in patients with schizophrenia in whom certain early disturbances of auditory message filtering have been found and may be associated with certain abnormalities which are particularly localised in the left temporal lobe. METHODS: Otoacoustic emissions, including click evoked and spontaneous emissions and measurements of functioning of the medial olivocochlear efferent system were obtained from 12 chronic schizophrenic patients and compared with normative data recorded from 12 normal controls. RESULTS: Otoacoustic emission amplitudes and medial olivocochlear functioning were similar between the normal controls and schizophrenic patients; the schizophrenic patients did, however, differ from the normal controls in otoacoustic emission intensity and in medial olivocochlear asymmetry. A tendency to a higher number of spontaneous peaks, and a significantly higher click evoked otoacoustic emission response amplitude were found in the right ear compared with the left ear of schizophrenic patients. For the medial olivocochlear system, whereas normal controls showed greater attenuation in the right than in the left ear, schizophrenic patients lacked such an asymmetry. CONCLUSION: In the absence of any attention task, the findings show disturbed peripheral lateralisation in schizophrenia of mechanisms involved in auditory information filtering. Such a lack of right ear advantage in medial olivocochlear functioning may thus be a peripheral reflection of central lateralisation anomalies.

Acoustic Stimulation↗
PubMed2000

Cognitive sequence processing and syntactic comprehension in schizophrenia.

It has been repeatedly demonstrated that schizophrenic patients are impaired in the comprehension of sentences with complex syntax. We investigated the hypothesis that this syntactic comprehension impairment in schizophrenia is not a purely linguistic dysfunction, but rather the reflection of a cognitive sequence processing impairment that is revealed as task complexity increases. We tested 10 schizophrenic patients using a standard measure of syntactic comprehension, and a non-linguistic sequence processing task, both of which required simple and complex transformation processing. Patients' performance impairment on the two tasks was highly correlated (r2 = 0.84), and there was a significant effect for complexity, independent of the task. These results are quite similar to those of aphasic patients with left hemisphere lesions. This suggests that syntactic comprehension deficits in schizophrenia reveal the dysfunction of cognitive sequence processing mechanisms that can be expressed both in linguistic and non-linguistic sequence tasks.

Adult↗
PubMed2000

Confusion between silent and overt reading in schizophrenia.

The present study was aimed at investigating whether schizophrenic patients are impaired in monitoring their own speech. In particular, we attempted to assess their ability to discriminate between overt and covert speech in a reading task, in order to verify whether they can correctly recollect the modality in which an internally generated action is produced. Subjects were asked to read either silently or aloud, items from a list of words. After a delay of 5 min, they were required to indicate in a new list which words had been read previously (either silently or overtly), or had never been presented during the reading task. With respect to normal controls, schizophrenic patients showed a significant bias to report that they had read aloud words which they had actually read silently, or which were absent during the reading task. The results are discussed in relation to recent neuroimaging studies on inner and overt speech in hallucinating schizophrenic patients. Our data favour the hypothesis that the inability to correctly discriminate between inner and overt speech may play a role in the onset of schizophrenic hallucinations.

Adult↗
PubMed1998

Gaze discrimination is unimpaired in schizophrenia.

Interpersonal communication is largely dependent on interpretation of facial expression and emotion. Difficulties in face processing, and more specifically in gaze discrimination, have been described in schizophrenic patients. According to Baron-Cohen (Mindblindness. M.I.T. Press, Cambridge, MA, 1995), gaze discrimination relies on the functioning of a specific cognitive module, the Eye Direction Detector (EDD). It has been proposed [Rosse et al. (1994) Gaze discrimination in patients with schizophrenia: preliminary report. American Journal of Psychiatry 151, 919-921] that an impairment in gaze discrimination is present in schizophrenia, and plays a fundamental role in inducing the paranoid symptoms reported by many patients. However, in the previous studies, gaze direction detection and interpretation of gaze have never been completely dissociated. The present experiment attempts to test the schizophrenics' skill in a simple gaze direction detection task. A series of photographic portraits of models looking at different directions have been presented to 22 schizophrenic patients and 36 control subjects. For each portrait subjects were asked to determine whether gaze was directed to the right or to the left by pressing a keyboard key. A forced choice paradigm was used. No differences were reported between schizophrenic patients and control subjects. That is, in the present paradigm, schizophrenic patients did not show any specific impairment in detecting the direction of gaze of the portraits. The results are discussed according to the notion that a dissociation is present in schizophrenia between implicit and explicit processes. The present case illustrates how the more automatic elementary functions, such as the detection of gaze direction, may be spared in schizophrenic patients, whereas explicit cognitive functions are likely more affected.

Adult↗
PubMed1998

Semantic priming in major depressive state.

We studied semantic priming in 20 major depressive subjects. The methodology used was a visual lexical decision task. Semantic priming is the facilitation of target word recognition (shortening of response time) by the prior presentation of a semantically related context (a prime word). It relies on semantic processing of words and context, facilitating early cognitive stages of response. Varying the temporal interval between prime and target words onset allows us to distinguish between two priming mechanisms, relying on more automatic (test 1) or more controlled (i.e. attention dependent) (test 2) information processing. We observe a significant retardation for words and pseudo-words in depressives (in relation to controls) in both tests. In spite of a general retardation and increase of response times in depressives, semantic priming is evident in both groups and both tests, and does not differ significantly between depressive and control groups in either automatic or controlled conditions. Theses results confirm that semantic processing is not impaired in depression, and are discussed with regard to the hypothesis of an effortful processing impairment in depression, and to depressive retardation.

Adult↗
PubMed1998

Anomia in major depressive state.

Anomia, or word finding difficulty, is a frequent clinical symptom of the depressive state. This study investigates naming and lexicalization processes (or word production processes) in 11 depressive patients (major depressive state), through a picture naming task of 53 images corresponding to low frequency words. Depressives showed significantly more anomia and made more naming errors (semantically related substitution words) than control subjects. Tip-of-the-tongue (TOT) states, which correspond to an impairment at a later stage of phonological encoding with partial activation of phonological shape, remained rare in depressives despite the increase of lexicalization difficulties observed. Anomia observed in depressives could thus be related to an impairment at the early stage of lexicalization or word production processes (pre-phonological item selection and access, or storage of the semantic lexical item in Working Memory for further phonological encoding), without lexical-semantic disorganization. We discuss the relationship between such an elementary speech production disorder and cognitive impairments demonstrated in the depressive state (deficit of effortful and attentional processes, impairment in activation or initiation of cognitive processes and responses).

Adult↗
PubMed1998

Beyond consciousness of external reality: a "who" system for consciousness of action and self-consciousness.

This paper offers a framework for consciousness of internal reality. Recent PET experiments are reviewed, showing partial overlap of cortical activation during self-produced actions and actions observed from other people. This overlap suggests that representations for actions may be shared by several individuals, a situation which creates a potential problem for correctly attributing an action to its agent. The neural conditions for correct agency judgments are thus assigned a key role in self/other distinction and self-consciousness. A series of behavioral experiments that demonstrate, in normal subjects, the poor monitoring of action-related signals and the difficulty in recognizing self-produced actions are described. In patients presenting delusions, this difficulty dramatically increases and actions become systematically misattributed. These results point to schizophrenia and related disorders as a paradigmatic alteration of a "Who?" system for self-consciousness.

Cerebral Cortex↗
PubMed1997

Schizophrenics learn surface but not abstract structure in a serial reaction time task.

We investigated the hypothesis that explicit cognitive processing is impaired in schizophrenia, while implicit processing is left largely intact, using a single sequence learning paradigm that simultaneously measures surface and abstract structure learning. Surface structure is the serial order of sequence elements. Abstract structure is defined in terms of the relationships between repeating elements. Sequences ABCBAC and DEFEDF thus share the same abstract structure, with different surface structures. Learning abstract structure requires explicit processing, while surface structure can be learned in implicit conditions. We predict however, that in explicit conditions, schizophrenics should learn surface structure but not abstract structure. Indeed, schizophrenic patients learned surface structure, but failed to learn abstract structure, demonstrating that implicit sequence processing is spared in schizophrenia while explicit sequence processing is impaired.

Adult↗
PubMed1997

Looking for the agent: an investigation into consciousness of action and self-consciousness in schizophrenic patients.

The abilities to attribute an action to its proper agent and to understand its meaning when it is produced by someone else are basic aspects of human social communication. Several psychiatric syndromes, such as schizophrenia, seem to lead to a dysfunction of the awareness of one's own action as well as of recognition of actions performed by others. Such syndromes offer a framework for studying the determinants of agency, the ability to correctly attribute actions to their veridical source. Thirty normal subjects and 30 schizophrenic patients with and without hallucinations and/or delusional experiences were required to execute simple finger and wrist movements, without direct visual control of their hand. The image of either their own hand or an alien hand executing the same or a different movement was presented on a TV-screen in real time. The task for the subjects was to discriminate whether the hand presented on the screen was their own or not. Hallucinating and deluded schizophrenic patients were more impaired in discriminating their own hand from the alien one than the non-hallucinating ones, and tended to misattribute the alien hand to themselves. Results are discussed according to a model of action control. A tentative description of the mechanisms leading to action consciousness is proposed.

Adult↗
PubMedDate not supplied

[Basic cognitive-perceptive module in schizophrenics].

A specific deficit in gaze discrimination has been hypothesized for schizophrenic patients (Rosse et al., 1994). Gaze discrimination is a basic ability for animals as well as for human beings. It plays an important role in mutual control of social interactions. According to Baron-Cohen (1995), sensitivity to eye gaze relies on a specific cognitive module, the Eye Direction Detector (EDD). The author distinguishes three basic functions of the EDD; first, the EDD is involved in eyes detection; second, the EDD is used in order to establish direction of gaze, and specially to compute whether the eyes one is looking at are directed to the subject or somewhere else; third, the EDD is implied in interpretation of gaze as seeing. Rosse et al. (1994) tested subjective impressions concerning gaze discrimination in a group of schizophrenic patients. Schizophrenics reported the subjective impression of being looked at by the portraits significantly more often than controls. The authors concluded that a specific impairment in gaze detection is present in the patients, and that it may be responsible for the paranoid symptoms often reported in schizophrenia. However, it seems difficult to assert that a response bias in schizophrenics toward perceiving faces as looking at them results from the deficit of an elementary perceptual module responsible for the detection of eye-direction. Rather we suspect such a bias to be the consequence of an impairment of the more complex level of mindreading, responsible for the interpretation of gaze as seeing in terms of mental states. The aim of the present experiment was to test in a more specific way the elementary gaze discrimination system. A series of portraits of models looking at five different directions (-30 degrees, -15 degrees, 0 degree, 15 degrees, 30 degrees), have been presented to 22 schizophrenic patients and 36 normal control subjects. In each trial one portrait was presented. Subjects were asked to determine the direction of its gaze by pressing the "z-key" (left side of the keyboard) if the portrait was looking to the left, and the "/-key" (right side of the keyboard) if the portrait was looking to the right. For each trial, we recorded both the side of the response (left key or right key) and the corresponding reaction time (RT). For the purpose of the analysis, the mean numbers of left responses were computed for each subject. The mean numbers of left responses recorded for each direction of gaze did not significantly differ between patients and controls. That is schizophrenic patients are not impaired in the gaze discrimination task used in the present study. In Rosse's experiment, subjects were required to decide whether the portrait on the screen was looking at them or not. On the contrary, in our task, subjects were simply required to state whether gaze was directed to the right or to the left. No explicit judgment was required as to whom or what gaze was directed. Therefore, we can assume that the present paradigm investigated the functioning of a more basic process than that tested by Rosse et al. Our data are consistent with those reporting that basic cognitive processes are unimpaired in schizophrenia, whereas explicit processes are extensively affected.

Adult↗