Thalamic thought disorder: on being "a bit addled"

Kraepelin's schizophasia: Chaotic speech with preservation of comprehension and activities of daily living

BACKGROUND

In his classic account of dementia praecox Kraepelin reserved a few pages for a small number of psychotic patients with disorganized speech but who retained the ability to cope with their daily lives.

CASE REPORT

A 49-year-old homemaker has been suffering from a continuous hallucinatory-delusional state since she was 24 years old. Her verbal and written language was chaotic and full of neologisms, but fluent and grammatically correct. Speech disorganization was roughly proportional to the need to express ideas and thoughts through creative speech. She followed verbal, written, and visuo-gestural commands and flawlessly repeated words and sentences of variable length. She read aloud and discussed the news properly. She ran the house, cooked for her relatives, and went to the supermarket and the bank alone. She knew the prices of common goods and handled money with ease. The unique coexistence of (i) chaotic speech, (ii) preservation of aural, written, and gestural comprehension, and (iii) organized non-verbal behavior, in patients (iv) in a chronic delusional-hallucinatory state is the hallmark of the syndrome of "schizophasia" originally described by Kraepelin. The main features of Kraepelin's schizophasia are vividly illustrated by videos and photos of the patient during her daily life.

DISCUSSION

The differential diagnosis of schizophasia is reviewed, especially with the sensory aphasias (Wernicke's and transcortical), from which the confusional speech of our patient was differentiated by her preserved ability to repeat and understand spoken and written language. Because her primary language abilities were spared, the cardinal deficit seems to lie at the interface where thoughts and ideas are encoded into expressive language.

CONCLUSION

The expression "Kraepelin's schizophasia" should be restricted to the speech-behavioral dissociation first observed by Kraepelin in chronic psychotic patients. The term "schizophasia", in turn, should be kept as a generic designation for any language alteration in schizophrenia.

Involvement of Thalamocortical Networks in Patients With Poststroke Thalamic Aphasia

BACKGROUND AND OBJECTIVE

Theories assume that thalamic stroke may cause aphasia because of dysfunction in connected cortical networks. This takes into account that brain functions are organized in distributed networks, and in turn, localized damage may result in a network disorder such as thalamic aphasia. With this study, we investigate whether the integration of the thalamus into specific thalamocortical networks underlies symptoms after thalamic stroke. We hypothesize that thalamic lesions in patients with language impairments are functionally connected to cortical networks for language and cognition.

METHODS

We combined nonparametric lesion mapping methods in a retrospective cohort of patients with acute or subacute first-ever thalamic stroke. A relationship between lesion location and language impairments was assessed using nonparametric voxel-based lesion-symptom mapping. This method reveals regions more frequently damaged in patients with compared with those without a symptom of interest. To test whether these symptoms are linked to a common thalamocortical network, we additionally performed lesion-network-symptom mapping. This method uses normative connectome data from resting-state fMRI of healthy participants (n = 65) for functional connectivity analyses, with lesion sites serving as seeds. Resulting lesion-dependent network connectivity of patients with language impairments was compared with those with motor and sensory deficits as baseline.

RESULTS

A total of 101 patients (mean [SD] age 64.1 [14.6] years, 57 left, 42 right, and 2 bilateral lesions) were included in the study. Voxel-based lesion-symptom mapping showed an association of language impairments with damage to left mediodorsal thalamic nucleus lesions. Lesion-network-symptom mapping revealed that language compared with sensory deficits were associated with higher normative lesion-dependent network connectivity to left frontotemporal language networks and bilateral prefrontal, insulo-opercular, midline cingular, and parietal domain-general networks. Lesions related to motor and sensory deficits showed higher lesion-dependent network connectivity within the sensorimotor network spanning prefrontal, precentral, and postcentral cortices.

DISCUSSION

Thalamic aphasia relates to lesions in the left mediodorsal thalamic nucleus and to functionally connected left cortical language and bilateral cortical networks for cognitive control. This suggests that dysfunction in thalamocortical networks contributes to thalamic aphasia. We propose that inefficient integration between otherwise undamaged domain-general and language networks may cause thalamic aphasia.

Brain and language: evidence for neural multifunctionality

This review paper presents converging evidence from studies of brain damage and longitudinal studies of language in aging which supports the following thesis: the neural basis of language can best be understood by the concept of neural multifunctionality. In this paper the term "neural multifunctionality" refers to incorporation of nonlinguistic functions into language models of the intact brain, reflecting a multifunctional perspective whereby a constant and dynamic interaction exists among neural networks subserving cognitive, affective, and praxic functions with neural networks specialized for lexical retrieval, sentence comprehension, and discourse processing, giving rise to language as we know it. By way of example, we consider effects of executive system functions on aspects of semantic processing among persons with and without aphasia, as well as the interaction of executive and language functions among older adults. We conclude by indicating how this multifunctional view of brain-language relations extends to the realm of language recovery from aphasia, where evidence of the influence of nonlinguistic factors on the reshaping of neural circuitry for aphasia rehabilitation is clearly emerging.

Thalamic mechanisms in language: a reconsideration based on recent findings and concepts

Recent literature on thalamic aphasia and thalamic activity during neuroimaging is selectively reviewed followed by a consideration of recent anatomic and physiological findings regarding thalamic structure and functions. It is concluded that four related corticothalamic and/or thalamocortical mechanisms impact language processing: (1) selective engagement of task-relevant cortical areas in a heightened state of responsiveness in part through the nucleus reticularis (NR), (2) passing information from one cortical area to another through corticothalamo-cortical mechanisms, (3) sharpening the focus on task-relevant information through corticothalamo-cortical feedback mechanisms, and (4) selection of one language unit over another in the expression of a concept, accomplished in concert with basal ganglia loops. The relationship and interaction of these mechanisms is discussed and integrated with thalamic aphasia and neuroimaging data into a theory of thalamic functions in language.

Cognitive, affective and behavioural disturbances following vascular thalamic lesions: a review

During the last decades, many studies have shown that the thalamus is crucially involved in language and cognition. We critically reviewed a study corpus of 465 patients with vascular thalamic lesions published in the literature since 1980. 42 out of 465 (9%) cases with isolated thalamic lesions allowed further neurocognitive analysis. On the neurolinguistic level, fluent output (=31/33; 93.9%), normal to mild impairment of repetition (=33/35; 94.3%), mild dysarthria (=8/9; 88.9%) and normal to mild impairment of auditory comprehension (=27/34; 79.4%) were most commonly found in the group of patients with left and bilateral thalamic lesions. The taxonomic label of thalamic aphasia applied to the majority of the patients with left thalamic damage (=7/11; 63.6%) and to one patient with bithalamic lesions (=1/1). On the neuropsychological level, almost 90% of the left thalamic and bithalamic patient group presented with amnestic problems, executive dysfunctions and behaviour and/or mood alterations. In addition, two thirds (2/3) of the patients with bilateral thalamic damage presented with a typical cluster of neurocognitive disturbances consisting of constructional apraxia, anosognosia, desorientation, global intellectual dysfunctioning, amnesia, and executive dysfunctions associated with behaviour and/or mood alterations. Our study supports the long-standing view of a 'lateralised linguistic thalamus' but restates the issue of a 'lateralised cognitive thalamus'. In addition, critical analysis of the available literature supports the view that aphasia following left or bithalamic damage constitutes a prototypical linguistic syndrome.

Two new scales of formal thought disorder in schizophrenia

Information provided by patients and respective carers may help to understand formal thought disorder (FTD) in schizophrenia. Two scales, one for patients (FTD-patient) and one for carers (FTD-carer), were constructed to assess pragmatics, cognitive, paralinguistic, and non-verbal aspects of communication. In the first scale the patients themselves assess their verbal communication; in the second scale the carer assesses the speech of the respective patient. Both scales exhibited internal reliability and evidence of good test-retest reliability. Higher total scores on both scales (FTD-patient and FTD-carer) were significantly associated with positive FTD, but not with negative FTD. Principal component analysis of the scales yielded a multidimensional structure. It is suggested that FTD in schizophrenia may be associated with a range of deficits (e.g. pragmatics, lexical activation, working memory, sustained attention). These scales, in conjunction with the clinician's assessment, can provide a more comprehensive picture of FTD in schizophrenia, revealing its dimensions and making it possible to establish associations between symptoms of FTD and neuropsychological, neurophysiologic, and neuroimaging data. In addition, they provide service users' and carers' perspectives for the assessment of communication in schizophrenia.

Evolution of Neurological, Neuropsychological and Sleep-Wake Disturbances After Paramedian Thalamic Stroke

Background and Purpose— The clinical features and natural course of paramedian thalamic stroke is poorly known. The aim of this study was to characterize the evolution of neurological, neuropsychological, and sleep–wake deficits after paramedian thalamic stroke.

Methods— Forty-six consecutive patients, aged 48.4±16.6 years, were studied. Fourteen had bilateral, 16 left-sided, and 16 right-sided lesions. Assessment included neurological examinations, estimation of sleep needs, formal neuropsychological tests (n=27), and polysomnographies (n=31). Functional outcome was followed up over 1 year in 31 patients with the modified Rankin Scale and Barthel index.

Results— Oculomotor palsy (76% of patients), mild gait ataxia (67%), deficits of attention (63%), fluency and error control (59%), learning and memory (67%), and behavior (67%) were common in the acute stroke phase. Outcome was excellent with right-sided infarcts but mostly incomplete with bilateral and left-sided lesions. This was mainly related to persistent frontal lobe-related and cognitive deficits found in 100% bilateral and 90% left-sided, but only 33% right-sided strokes. Initially, hypersomnia was present in all patients associated with increased stage 1 sleep, reduced stage 2 sleep, and reduced sleep spindles. Sleep needs improved in patients with bilateral and almost disappeared with unilateral lesions after 1 year. Sleep architecture remained abnormal with the exception of sleep spindles that increased.

Conclusions— Whereas neurological deficits and hypersomnia recover to large extent in patients with paramedian thalamic stroke, the frontal lobe-related and cognitive deficits, which are mainly linked with bilateral and left-sided lesions, often persist. As such, stroke outcome is better in right-sided than bilateral or left-sided infarcts.

Impairments of procedures for implementing complex language are due to disruption of frontal attention processes

Production of complex discourse-lengthy, open-ended utterances and narratives-requires intact basic language operations, but it also requires a series of learned procedures for construction of complex, goal-directed communications. The progression of clinical disorders from transcortical motor aphasia to dynamic aphasia to discourse impairments represents a progression of procedural deficits from basic morpho-syntax to complex grammatical structures to narrative and a progression of lesions from posterior frontal to polar and/or lateral frontal to medial frontal. Two cases of impaired utilization of language exemplify the range of impairments from clearly aphasic agrammatic, nonfluency to less and less "aphasic" and more and more executive impairments from transcortical motor aphasia to dynamic aphasia to narrative discourse disorder. The clinical phenomenology of these disorders gradually comes to be more accurately defined in the terminology of executive deficits than that of aphasia. The executive deficits are, in turn, based on impairments in various components of attention. Specific impairments in energizing attention and setting response criteria associated, respectively, with lesions in superior medial and left ventrolateral frontal regions may cause defective recruitment of the procedures of complex language assembly.

Distinct neuropsychological characteristics in Creutzfeldt-Jakob disease

OBJECTIVES

To characterise the nature of cognitive change in Creutzfeldt-Jakob disease (CJD).

METHODS

Case histories are reported of four patients with sporadic (sCJD) and two with familial CJD (fCJD), with postmortem pathological findings in four cases. The data derived from cognitive examination are examined with respect to the presence or absence of a variety of characteristics to elicit performance profiles across cognitive domains.

RESULTS

Three patients with sCJD exhibited clear focal cortical deficits. One patient had visual impairment leading to cortical blindness, associated with posterior hemisphere abnormalities on single photon emission computed tomography (SPECT) imaging; two others had impairments in language, mirrored by left hemisphere SPECT abnormalities. The remaining three patients showed no specific cortical symptomatology. Despite these differences all six patients shared common qualitative characteristics: episodic unresponsiveness, interference effects, and profound verbal and motor perseveration. These common features are interpreted in terms of impaired activation and regulation of neocortex from subcortical structures. Findings from postmortem pathological examination and from the published literature provide converging evidence to implicate a critical role of the thalamus.

CONCLUSION

These preliminary findings suggest that sCJD and fCJD may be associated with distinct neuropsychological characteristics.

Neuropsychological consequences of right thalamic haemorrhage: case study and review

The neuropsychological performance of a right-handed man is examined following haemorrhage from the anterior sections of the right thalamus. A pattern of temporally graded retrograde amnesia, global anterograde amnesia, impaired short-term memory, behavioural changes, and severe executive deficits were identified. The deficits evident in this case are discussed in reference to existing neuropsychological literature regarding the consequences of thalamic infarction. It is proposed that damage to the anterior thalamic nuclei results in a frontal dysexecutive syndrome and that such a dysexecutive syndrome can explain the neuropsychological deficits observed in this case.

Mania caused by a diencephalic lesion

We describe the case of a young male patient, SN, who suffered a MR-documented ischaemic lesion of both dorsomedial thalami and presented with a transient maniform syndrome. SN's neuropsychological, structural and functional imaging findings are compared with similar reported cases and are discussed in the framework of fronto-subcortical circuits and their proposed behavioural disorders. SN's mania was characterized by restlessness, mood elevation, a tendency for pleasurable activities, inflated self-esteem and loss of disease awareness. Other symptoms were sexual disinhibition, tactlessness, abnormal discourse, and reduced need for food and sleep. His neuropsychological assessment revealed an anterograde amnesia, and an impairment of frontal-executive functions. A SPECT-study showed diaschisis-related areas of hypoperfusion in both prefrontal regions which were interpreted as equivalents of SN's frontal-dysexecutive syndrome. In addition, there was a perfusion deficit in the right orbitofrontal cortex, which was taken as the imaging correlate of SN's secondary mania and personality disorder. These findings suggest that SN's mania and his other symptoms result from the twofold disruption of fronto-subcortical connections, namely of the right orbitofrontal loop which is concerned with mood regulation and socially appropriate behaviour, and of the dorsolateral prefrontal loop which mediates executive cognitive functions.

A major role for thalamocortical afferents in serotonergic hallucinogen receptor function in the rat neocortex

Activation of 5-hydroxytryptamine(2A) (5-HT(2A)) receptors by hallucinogenic drugs is thought to mediate many psychotomimetic effects including changes in affect, cognition and perception. Conversely, blockade of 5-HT(2A) receptors may mediate therapeutic effects of many atypical antidepressant and antipsychotic drugs. The purpose of the present study was to determine the source of subcortical glutamatergic afferents, which would project widely throughout the anterior-posterior axis of the rat brain to the apical dendrites of layer V pyramidal cells of the medial prefrontal cortex, from which serotonin induces transmitter release via activation of 5-HT(2A) receptors. Fiber-sparing chemical lesions of the medial thalamus selectively decreased the frequency of serotonin-induced excitatory postsynaptic currents recorded from layer V pyramidal cells in the prelimbic region of the medial prefrontal cortex by 60%. In contrast, large bilateral lesions of the amygdala did not alter the serotonin response. These thalamic lesions significantly decreased the amount of binding to either mu-opioid or metabotropic glutamate 2/3 receptors in the prelimbic region of the medial prefrontal cortex as expected from previous evidence that these agonists for these receptors suppress serotonin-induced excitatory postsynaptic currents by a presynaptic mechanism. Surprisingly, the amount of specific binding to cortical 5-HT(2A) receptors was significantly increased by the medial thalamic lesions. Thus, these experiments demonstrate that activation of cortical 5-HT(2A) receptors modulates transmitter release from thalamocortical terminals. Unexpectedly, lesioning the thalamocortical terminals also alters 5-HT(2A) receptor binding in the prefrontal cortex. These findings are of interest with respect to understanding therapeutic effects of antidepressant/antipsychotic drugs and the known behavioral effects of thalamic lesions in humans.

Effects of intralaminar thalamic lesions on sensory attention and motor intention in the rat: a comparison with lesions involving frontal cortex and hippocampus

A self-paced serial reaction task was developed to differentiate between the effects of intralaminar thalamic lesions on sensory attention and intentional motor function. Results were compared for hippocampal and frontal cortical lesions to test for the possible involvement of pathways involving these parts of the brain in any impairments associated with the thalamic lesion. Lesions of the intralaminar thalamic nuclei affected response latency without affecting accuracy. This increase in latency was unaffected by variations in stimulus duration, even though this manipulation had a substantial effect on response accuracy. Intralaminar lesions did not affect the response to distracting stimuli or to manipulations of stimulus salience. Thus it seems unlikely that the effects of intralaminar lesions on motor function were related to sensory loss or attentional dysfunction. Hippocampal lesions had no significant effect on any measure of performance. Frontal cortical lesions were associated with an increase in latency comparable to the intralaminar group and also affected the accuracy of responding to brief stimuli or under conditions of reduced stimulus salience. These results are discussed in light of evidence that lesions of the intralaminar nuclei affect functions mediated by anatomically related areas of frontal cortex and striatum.

Language and space: some interactions

Is language linked to mental representations of space? There are several reasons to think that language and space might be separated in our cognitive systems, but they nevertheless interact in important ways. These interactions are evident in language viewed as a means of communication and in language considered a form of representation. In communication, spatial factors may be explicit in language itself, such as the spatial-gestural system of American Sign Language. Even the act of conversing with others is a spatial behavior because we orient to the locations of other participants. Language and spatial representations probably converge at an abstract level of concepts and simple spatial schemas.

Reduced number of mediodorsal and anterior thalamic neurons in schizophrenia

BACKGROUND

The thalamus is a brain region of interest in the study of schizophrenia because it provides critical input to brain regions such as the prefrontal, cingulate, and temporal cortices, where abnormalities have been repeatedly observed in patients with schizophrenia. Postmortem anatomic studies have rarely investigated the thalamus in this population.

METHODS

Postmortem tissue was obtained from the left hemisphere of eight male schizophrenic patients and eight male age-matched control subjects. The optical dissector stereologic procedure was used to count neurons in the mediodorsal (MD) and anteroventral/anteromedial (AV/AM) nuclei of the thalamus.

RESULTS

The number of neurons and volume of the MD were significantly reduced by 35% and 24%, respectively. The MD cell number reduction was a consistent finding; every control subject had more and every schizophrenic subject had fewer than 3.5 million neurons. Neuron number was also significantly reduced (16%) in the AV/AM nuclei.

CONCLUSIONS

The present data indicate that schizophrenia is associated with robust reductions in nerve cell numbers in nuclei that communicate with the prefrontal cortex and limbic system. These thalamic anatomic deficits may be responsible, in part, for previous reports of such prefrontal cortical abnormalities as reduced synaptic density, reduced volume, and metabolic hypofunction.