Biomedical subjects

Indira Tendolkar

Publications and source records attributed to Indira Tendolkar.

10 recordsLinked to original sources

PubMed2026

Transcranial Magnetic Stimulation for Patients with Exposure Therapy Resistant Obsessive-Compulsive Disorder (TETRO): Study Protocol for a Multicenter Randomized Controlled Trial.

BACKGROUND: Obsessive-compulsive disorder (OCD) is a disabling mental disorder, characterized by obsessions, compulsions, and substantial morbidity. Approximately 50% of adults with OCD fail to achieve satisfactory outcomes from first-line treatments, such as exposure therapy with response prevention (ERP), with or without medication. This leads to chronic social, educational, and occupational impairment. While invasive procedures such as deep brain stimulation are available for severe, treatment-refractory cases, a need remains for less invasive alternatives. Repetitive transcranial magnetic stimulation (rTMS), a noninvasive intervention, shows promise in reducing OCD symptoms. Unlike in depression, rTMS is not yet reimbursed for OCD in the Dutch healthcare system. OBJECTIVE: This study examines the efficacy and cost-effectiveness of low-frequency (1Hz) rTMS targeting the presupplementary motor area (pre-SMA) compared to sham rTMS as an adjuvant treatment to ERP in adults with OCD with inadequate response to first-line treatment. METHODS: A total of 250 adults with OCD will be enrolled in this multicenter randomized controlled trial. Participants will be randomly assigned to ERP combined with either active or sham 1Hz rTMS over the pre-SMA. Treatment is administered 4 times weekly for at least 5 weeks (20 rTMS-ERP sessions), with optional extension of 1 to 2 weeks, up to 28 rTMS-ERP sessions. Clinical assessments occur at baseline, weekly during treatment, posttreatment, and at 3, 6, and 12 months follow-up. Participants undergo pre- and posttreatment (functional) (MRI) scans, including a symptom provocation task. Blood sampling takes place pre- and posttreatment and at 3-month follow-up. The primary outcome is OCD severity at posttreatment, as measured by the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS). Secondary outcomes include functional improvement, quality of life, and societal costs. Pretreatment symptom profiles, genotype, and brain network topology will be analyzed as predictors of response and relapse risk. Pre-to-post treatment change in blood-based and magnetic resonance (MR)-based neuroplasticity markers will help explore differential mechanisms between ERP alone and combined rTMS-ERP. We expect that the verum rTMS protocol will be cost-effective compared to sham-rTMS. RESULTS: Recruitment started in April 2022, and as of February 2026, 201 participants have been enrolled. Posttreatment assessments are projected to be completed in December 2026, with final one-year follow-up evaluations anticipated by the end of 2027. CONCLUSIONS: To our knowledge, this study is the first adequately powered randomized controlled trial examining efficacy, cost-effectiveness, and mechanism of action of rTMS for OCD as adjuvant therapy to ERP. In case of efficacy and/or cost-effectiveness, it will pave the way for rTMS as insured health care for adults with OCD in the Netherlands, and possibly other European countries. Furthermore, this trial will provide insight into the mechanisms of treatment response to intensive ERP, with and without adjunctive rTMS, as well as potential side effects, individual variability, and long-term outcomes in adults with OCD.

Humans↗

PubMed2006

The rhinal cortex: 'gatekeeper' of the declarative memory system.

Almost all studies probing neural activity underlying the declarative memory system in humans have investigated either memory encoding or retrieval. Here, however, we suggest integrating encoding and retrieval operations into a single operation executed by the rhinal cortex. The more familiar an item is, the less rhinal processing it requires and the less vigorously it is encoded into memory. Given the anatomical position and the functional properties of the rhinal cortex, this operation fulfills an essential task: it optimally allocates limited encoding resources away from familiar information and towards novel information. We propose a rhinal processing stage that optimizes the declarative memory system by fully integrating encoding and retrieval operations into a single 'gatekeeper' operation.

Animals↗

PubMed2006

Neurocognitive functioning in subjects at risk for a first episode of psychosis compared with first- and multiple-episode schizophrenia.

Evidence from neurobiological studies suggests that schizophrenia arises from an early abnormality in brain development and possibly further progressive developmental mechanisms. Despite a delay between the acquisition of neuropathology and the triggering of psychosis, neurobiological susceptibility is likely to be expressed subclinically by biobehavioral markers in the premorbid stage. The exploratory study aims at identifying potential neurocognitive risk factors and investigating the unfolding of the illness within a cross-sectional design by comparing neurocognitive profiles in 179 healthy controls, 38 clinically identified subjects in an early initial prodromal state (EIPS) for psychosis, 90 subjects in a late initial prodromal state (LIPS), 86 first-episode patients with schizophrenia, and 88 multiple-episode patients. Subjects at risk were substantially impaired in verbal executive and verbal memory functions. Compared to EIPS subjects, LIPS subjects demonstrated additional attentional deficits. Both EIPS and LIPS subjects were superior to first-episode patients who presented a generalized neuropsychological deficit profile, and to multiple-episode patients who showed evidence for further decline. Although results were influenced by general intellectual abilities and demographic and clinical characteristics, they could not account for total group differences. Results support a neurodevelopmental model of psychosis with further progressive mechanisms and are consistent with a primary involvement of left frontotemporal networks in the prodromal phase.

Adult↗

PubMed2005

Impaired mismatch negativity generation in prodromal subjects and patients with schizophrenia.

BACKGROUND: Mismatch negativity (MMN) specifically the response to tone duration deviants has consistently been shown to be reduced in schizophrenia suggesting dysfunction in auditory sensory memory. As part of a multidimensional approach to the early recognition of psychosis, MMN was investigated as a possible risk factor for later development of psychosis in subjects with a prodromal syndrome. Forty-three prodromal subjects, 31 neuroleptic-free inpatients with schizophrenia and 33 healthy controls were studied. A prodromal state was defined by a cluster 'Cognitive Disturbances' as defined by the 'Bonn Scale for the Assessment of Basic Symptoms' (BSABS), which was found highly predictive of first-episode schizophrenia. To elicit MMN, a three-tone auditory oddball paradigm with 10% 'duration deviants' and 10% 'frequency deviants' was used. RESULTS: MMN amplitudes to tone duration deviants were significantly reduced in the patients with schizophrenia compared to controls. The putatively prodromal subjects also showed a slight, though non-significant reduction of the MMN amplitude that was intermediate between normal controls and patients with schizophrenia, and with a larger within-group variance. CONCLUSION: These results support the view that abnormalities in temporal processing are particularly pronounced in patients with schizophrenia. Prodromal subjects are a heterogeneous group with regard to outcome and time until transition to a first psychotic episode. Follow-up of these putatively prodromal subjects will show whether MMN amplitudes further reduce over time in those developing psychosis and if a reduction is state-dependent.

Acoustic Stimulation↗

PubMed2005

Neural correlates of visuo-spatial attention during an antisaccade task in schizophrenia: an ERP study.

The authors investigated the role of visuo-spatial attention in an antisaccade task using event-related potentials (ERPs) in schizophrenia patients compared to healthy controls. ERPs between 80-130 ms (P100) after stimulus onset showed differences between pro- and antisaccades only for controls and can be related to the suppression of irrelevant stimulus features. Between 150-180 ms (N100), a larger amplitude for anti-compared to prosaccades over centroparietal electrodes showed that processes of visuo-spatial attention seem to be engaged in performance of the antisaccade task. Left temporo-occipitally, this activity was only evident in schizophrenia patients, possibly reflecting additional neuronal recruitment in order to perform the antisaccade task successfully.

Adult↗

PubMed2004

Process dissociation between contextual retrieval and item recognition.

We employed a source memory task in an event related fMRI study to dissociate MTL processes associated with either contextual retrieval or item recognition. To introduce context during study, stimuli (photographs of buildings and natural landscapes) were transformed into one of four single-color-scales: red, blue, yellow, or green. In the subsequent old/new recognition memory test, all stimuli were presented as gray scale photographs, and old-responses were followed by a four-alternative source judgment referring to the color in which the stimulus was presented during study. Our results suggest a clear-cut process dissociation within the human MTL. While an activity increase accompanies successful retrieval of contextual information, an activity decrease provides a familiarity signal that is sufficient for successful item recognition.

Adult↗

PubMed2004

Evidence for a dysfunctional retrosplenial cortex in patients with schizophrenia: a functional magnetic resonance imaging study with a semantic-perceptual contrast.

We investigated whether the retrosplenial and the posterior cingulate cortex (RS-PCC) is functionally impaired in schizophrenia patients. Therefore, we measured functional magnetic resonance imaging (fMRI) signal changes associated with a synonym-judgment task known to activate, among other areas, the RS-PCC. Compared to 12 matched control subjects, 12 schizophrenia patients exhibited reliably weaker activations in the RS-PCC, the dorsolateral prefrontal cortex and the left orbitofrontal cortex (P < 0.05, corrected). Differences in frontal activations are in line with previous studies showing a structurally and functionally affected prefrontal cortex in schizophrenia. The impaired RS-PCC functionality in a semantic task may relate to verbal memory deficits frequently observed in schizophrenia patients, because this region is pivotal for gating information into the medial temporal lobe memory system.

Brain Mapping↗

PubMed2004

Neural correlates of temporal context discrimination.

This study investigated event-related potential (ERP) effects when judgments about temporal context (recency judgments) required the retrieval of different amount of information. Subjects studied two consecutively presented word lists and at test made recency judgments to word pairs composed of two previously studied words, one drawn from each list ('Old + Old different' pairs), both drawn from the same list ('Old + Old same' pairs), or two unstudied words ('New + New' pairs). A frontopolar old/new effect was elicited by correct recency judgments which did not differ between both 'Old + Old' pairs. This finding suggests that the generators of the frontopolar old/new effect are not sensitive to the differing retrieval demands required here. However, an old/new effect over left inferior temporal electrodes was larger for 'Old + Old same' than for 'Old + Old different' pairs. The significance of these old/new effects are discussed in relation to the broader pattern of old/new effects seen in standard tests of declarative memory retrieval.

Adult↗

PubMed2003

Dimensions of working memory dysfunction in schizophrenia.

The aim of this study was to investigate the underlying structure of eight working memory tests used to assess prefrontal dysfunction in schizophrenia research [Letter-Number Span (LNS), Digit-Symbol Test (DST), Trail-Making Test B (TMT-B), Delayed Response Task (DRT) for spatial working memory, Subject Ordered Pointing Task (SOPT), Dual Tasking (DUAL), Continuous Performance Test (CPT)-Identical Pairs, Wisconsin Card Sorting Test (WCST)]. Sixty-six patients with schizophrenia showed significant working memory performance deficits in all tests when compared with 45 healthy controls. Performance was not systematically related to psychopathology. When differences in IQ were controlled, working memory deficits remained stable except in the WCST. Principal components analyses yielded three components for healthy controls: a comparator function of the central executive defined by a comparison of working memory content with information from the environment, an allocation of attentional resources function, and a maximum storage capacity function. The comparator and maximum storage functions could be replicated in the schizophrenia sample. However, the allocation function did not emerge as an independent component and was replaced by a component defined by the WCST. These findings suggest that working memory is not a unitary concept but rather should be conceptually differentiated as functions of transient storage/active rehearsal capacity and central executive manipulation supporting a previous suggestion proposed by Perry et al. [Schizophr. Bull. 27 (2001) 157].

Adult↗

PubMed2003

Menstrual cycle-dependent neural plasticity in the adult human brain is hormone, task, and region specific.

In rodents, cyclically fluctuating levels of gonadal steroid hormones modulate neural plasticity by altering synaptic transmission and synaptogenesis. Alterations of mood and cognition observed during the menstrual cycle suggest that steroid-related plasticity also occurs in humans. Cycle phase-dependent differences in cognitive performance have almost exclusively been found in tasks probing lateralized neuronal domains, i.e., cognitive domains such as language, which are predominantly executed by one hemisphere. To search for neural correlates of hormonally mediated neural plasticity in humans, we thus conducted a functional magnetic resonance imaging study measuring brain activity related to a semantic decision task in the language domain. This was contrasted with a letter-matching task in the perceptual domain, in which we expected no steroid hormone-mediated effect. We investigated 12 young healthy women in a counterbalanced repeated-measure design during low-steroid menstruation and high-steroid midluteal phase. Steroid serum levels correlated with the volume and lateralization of particular brain activations related to the semantic task but not with brain activity related to the perceptual task. More specifically, bilateral superior temporal recruitment correlated positively with progesterone and medial superior frontal recruitment with both progesterone and estradiol serum levels, whereas activations in inferior and middle frontal cortex were unaffected by steroid levels. In contrast to these specific interactions, testosterone levels correlated nonselectively with overall activation levels by neural and/or vascular factor(s). In conclusion, our data demonstrate steroid hormone responsivity in the adult human brain by revealing neural plasticity in the language domain, which appears hormone, task, and region specific.

Adult↗