Faulty suppression of irrelevant material in patients with thought disorder linked to attenuated frontotemporal activation.

Formal thought disorder is a feature schizophrenia that manifests as disorganized, incoherent speech, and is associated with a poor clinical outcome. The neurocognitive basis of this symptom is unclear but it is thought to involve an impairment in semantic processing classically described as a loosening of meaningful associations. Using a paradigm derived from the n400 event-related, potential, we examined the extent to which regional activation during semantic processing is altered in schizophrenic patients with formal thought disorder. Ten healthy control and 18 schizophrenic participants (9 with and 9 without formal thought disorder) performed a semantic decision sentence task during an event-related functional magnetic resonance imaging experiment. We employed analysis of variance to estimate the main effects of semantic congruency and groups on activation and specific effects of formal thought disorder were addressed using post-hoc comparisons. We found that the frontotemporal network, normally engaged by a semantic decision task, was underactivated in schizophrenia, particularly in patients with FTD. This network is implicated in the inhibition of automatically primed stimuli and impairment of its function interferes with language processing and contributes to the production of incoherent speech.

[The relationship between psychiatry and neurology]. / Das Verhältnis von Psychiatrie und Neurologie.

Neurology and psychiatry deal with diseases of the (central) nervous system. Historically neurological disorders are related to a proven organic basis, whereas psychiatric disorders are mainly defined by the phenomenology and course of the symptoms. Neuroscientific research methods such as molecular genetics, neurochemistry, neurophysiology, neuropathology, functional (SPECT, PET, fMRI) or structural (MRI) imaging have dramatically increased our knowledge of psychiatric and neurological disorders in the last 20 years. Accordingly diagnostic and therapeutic procedures and the long-term prognosis of numerous diseases in both disciplines have substantially improved (i.e. pharmacotherapy, psychotherapy, functional neurosurgery). For major brain disorders - such as dementia of the Alzheimer type - close collaboration between both disciplines is developing in diagnosis, therapy and care. Due to common neurobiological research topics, educational programs, medical training and the challenges of assuring appropriate care to patients with brain disorders, further cooperation between neurology and psychiatry is expected and necessary.

Reversed lateralization of temporal activation during speech production in thought disordered patients with schizophrenia.

BACKGROUND: Formal thought disorder is a core symptom of schizophrenia. It is associated with a reversed lateralization of the superior temporal cortex volume, an area that is implicated in lexical retrieval. We investigated the neural correlates of word retrieval during continuous speech in patients with formal thought disorder using functional magnetic resonance imaging (fMRI). METHODS: Blood oxygenation level dependent (BOLD) contrast was measured with fMRI while six patients with schizophrenia and six healthy control subjects spoke about seven Rorschach inkblots for 3 min each. Subjects produced varying amounts of speech during each run. In a within subject design, the number of words produced was correlated with the BOLD contrast in the two runs in each participant who showed the highest variance of speech output. RESULTS: In control subjects, the amount of speech produced was mainly correlated with activation in the left superior temporal gyrus. In the patient group, the main correlations were in the right superior temporal gyrus. CONCLUSIONS: During the production of continuous speech, patients with formal thought disorder showed a reversed laterality of activation in the superior temporal cortex. This is consistent with findings of perturbed hemispheric interaction in schizophrenia, particularly in patients with formal thought disorder.