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D J Veltman

Publications and source records attributed to D J Veltman.

11 recordsLinked to original sources
PubMed2001

Parahippocampal activation during successful recognition of words: a self-paced event-related fMRI study.

In this study, we investigated retrieval from verbal episodic memory using a self-paced event-related fMRI paradigm, similar to the designs typically used in behavioral studies of memory function. We tested the hypothesis that the medial temporal lobe (MTL) is involved in the actual recovery of verbal information (retrieval success) rather than in the attempt to retrieve information (retrieval attempt). To this end, we used a verbal recognition task, distinguishing correctly recognized words, correctly rejected words, and a low-level baseline condition. Directly contrasting correct recognition with correct rejection of words, we found activation in the left fusiform/parahippocampal gyrus, indicating that this region has a distinct role in the successful retrieval of verbal information. Furthermore, our results were in agreement with those of previous imaging studies that compared a fixed-paced verbal recognition task to a baseline condition, showing activation in bilateral inferior frontal cortex, left dorsolateral prefrontal cortex, left anterior insular cortex, and anterior cingulate. This demonstrates the applicability of a self-paced event-related design within imaging studies of memory function.

Adult↗
PubMed2000

Regionally specific sensitivity differences in fMRI and PET: where do they come from?

In this paper we report three neuroimaging studies of language that investigate potential sources of inconsistency in measured hemodynamic responses: (1) between sessions for fMRI, including differences in hormonal status, (2) between sessions for PET, and (3) between scanning modalities (PET and fMRI). Differences in evoked responses between sessions of the same modality were small. In particular we did not find any effect of hormone levels when testing during the first and third weeks of the menstrual cycle (although we cannot exclude the possibility that activation in the temporoparietal regions is sensitive to hormonal status). Comparing the two modalities showed that prefrontal regions were more activated in fMRI than in PET. This may relate to task switching between blocks in fMRI that is not induced by PET paradigms or increased error variance in these regions for PET. In contrast, temporal activations were found in PET more than in fMRI. We attribute the lack of temporal activations, in fMRI, to a combination of factors, including susceptibility artifacts, anticipatory activity during the control condition, discontinuous sampling of peristimulus time, and differences in the source, acquisition, and analysis of the measured signals. It is concluded that although there is sufficient reproducibility of results for these paradigms within each modality, the regionally specific differences in sensitivity found between modalities warrant further investigation. These regionally specific differences are important for a properly qualified interpretation of activation profiles in fMRI.

Adult↗
PubMed2000

Genetic studies of panic disorder: a review.

BACKGROUND: A review of the studies examining the genetic etiology of panic disorder shows the familial nature of the disorder and demonstrates that the etiology is greatly influenced by genetic factors. Strong evidence for vertical transmission in family studies led to molecular genetic studies, of which association designs appear promising, particularly when based on trait markers. DATA SOURCES: The MEDLINE and PsycLIT databases were searched for all reports published between 1966 and 2000 containing the keywords panic, genetic, twin, adoption, linkage, association, and QTL. CONCLUSION: We conclude that the multifactorial nature of panic disorder requires a multidisciplinary approach to gain insight into the determinants of the phenotype and the interaction of environmental and genetic factors.

Adoption↗
PubMed1999

Parametric fMRI analysis of visual encoding in the human medial temporal lobe.

A number of functional brain imaging studies indicate that the medial temporal lobe system is crucially involved in encoding new information into memory. However, most studies were based on differences in brain activity between encoding of familiar vs. novel stimuli. To further study the underlying cognitive processes, we applied a parametric design of encoding. Seven healthy subjects were instructed to encode complex color pictures into memory. Stimuli were presented in a parametric fashion at different rates, thus representing different loads of encoding. Functional magnetic resonance imaging (fMRI) was used to assess changes in brain activation. To determine the number of pictures successfully stored into memory, recognition scores were determined afterwards. During encoding, brain activation occurred in the medial temporal lobe, comparable to the results obtained by others. Increasing the encoding load resulted in an increase in the number of successfully stored items. This was reflected in a significant increase in brain activation in the left lingual gyrus, in the left and right parahippocampal gyrus, and in the right inferior frontal gyrus. This study shows that fMRI can detect changes in brain activation during variation of one aspect of higher cognitive tasks. Further, it strongly supports the notion that the human medial temporal lobe is involved in encoding novel visual information into memory.

Adult↗
PubMed1999

The critical relationship between the timing of stimulus presentation and data acquisition in blocked designs with fMRI.

This paper concerns the experimental design and statistical models employed by fMRI activation studies which block presentation of linguistic stimuli. In particular, we note that the relationship between the timing of stimulus presentation and data acquisition can have a substantial impact on the ability to detect activations in critical language areas, even when the stimuli are presented in blocks. Using a blocked word rhyming paradigm and repeated investigations on a single subject, activation was observed in Broca's area (left inferior frontal cortex) and Wernicke's area (left posterior temporoparietal cortex) when (i) the timing of data acquisition was distributed throughout the peristimulus time and (ii) an event-related analysis was used to model the phasic nature of the hemodynamic response within each block of repeated word stimuli. In contrast, when the timing of data acquisition relative to stimulus presentation was fixed, activation was detected in Broca's area but not consistently in Wernicke's area. Our results indicate that phasic responses to stimuli occur even in a blocked design and that the sampling and proper modeling of these responses can have profound effects on their detection. Specifically, distributed sampling over peristimulus time is essential in order to detect small activations particularly when they are transient. These findings are likely to generalize to the detection of transient signals in any cognitive paradigm.

Brain Mapping↗
PubMed1998

Predictability, controllability, and fear of symptoms of anxiety in epinephrine-induced panic.

BACKGROUND: Psychological manipulations (supplied information, safety cues) may influence panic rates during pharmacologic challenge tests in subjects with panic disorder (PD). Psychological panic models assume that fear of stress-related bodily sensations is central to the etiology of PD. METHODS: Prior to infusion of epinephrine, 50 subjects with PD were randomly assigned to one out of four experimental conditions: with or without extensive information and with or without external control, according to a 2 x 2 design. The panic rate was hypothesized to be lower in subgroups possessing extensive information and/or control. Fear of bodily sensations was used as a predictor. RESULTS: Thirty-four out of 50 patients (68%) panicked during the infusion. Subjects who received extensive information were marginally less likely to panic, but manipulation of control did not influence panic rates. Panickers did not differ from nonpanickers in measures of fear of fear. Anxiety sensitivity best predicted baseline anxiety and cognitive symptom scores, but was not associated with other outcome measures in panickers. Only baseline partial pressure of CO2 discriminated between panickers and nonpanickers. CONCLUSIONS: Manipulating external safety cues appears to be of limited value in modulating responses to epinephrine challenge. Together with our finding that fear of anxiety symptoms does not predict panic rates, these data argue against "fear of fear" as a key mechanism in epinephrine-induced panic.

Adult↗
PubMed1996

Epinephrine infusions in panic disorder: a double-blind placebo-controlled study.

Twenty-four subjects with Panic Disorder were infused with epinephrine in physiological doses or placebo according to a double-blind design. The panic rate in the epinephrine group (67%) was higher than in the placebo group (25%). Placebo panic occurred early during the procedure and was apparently associated with anticipation anxiety and stress-provoking situational factors. Panickers were characterized by a greater increase in heart rate as well as a drop in pCO2. Fear of bodily sensations was only weakly associated with state anxiety levels at point of panic. It is concluded that cognitive factors may not be important in epinephrine-induced panic.

Adult↗
PubMedDate not supplied

Epinephrine-induced panic attacks and hyperventilation.

To assess the effects of epinephrine on ventilation in patients with panic disorder and in social phobics, analyses were performed on pooled data from two previous infusion studies. Throughout the infusion, changes in transcutaneous PCO2 (tcPCO2), subjective anxiety, heart rate and blood pressure were recorded continuously. Twenty-nine patients received epinephrine, ten patients received placebo. Thirteen patients (45%) had a panic attack during epinephrine. The fall in tcPCO2 and the cardiovascular response was greater in panicking patients than patients who did not panic. Although the fall in tcPCO2 associated with panic was not substantial and did not indicate clinically significant acute hyperventilation, it appears to be a sensitive index for epinephrine-induced panic. The fall in tcPCO2 was predicted rather by the frequency of occurrence of anxiety-related somatic symptoms than by the fear of these symptoms. These findings further reduce a role for fear of bodily sensations in epinephrine-induced panic attacks and favor a biological sensitivity to sympathetic stimulation.

Adult↗
PubMedDate not supplied

Functional MR imaging in Alzheimer's disease during memory encoding.

BACKGROUND AND PURPOSE: We applied functional MR imaging with a learning task in healthy elderly volunteers and in patients with Alzheimer's disease to study brain activation during memory performance. The purpose was to determine the feasibility of functional MR imaging during a learning task in healthy elderly volunteers and in patients with Alzheimer's disease and to test our hypothesis that brain activation is decreased in the medial temporal lobe (MTL) memory system in patients with Alzheimer's disease compared with control volunteers. METHODS: In 12 patients with mild to moderate forms of Alzheimer's disease and 10 elderly control volunteers, activation of the MTL memory system was studied. We used two learning tasks that required the encoding of new information into memory. After the functional MR imaging experiment, participants were tested for recognition of the encoded objects. RESULTS: In the elderly control volunteers, activation during memory encoding was observed in medial and lateral temporal lobe structures (fusiform, parietal and occipital parts, and hippocampal formation) and in the frontal cortex, as reported previously in studies of young control volunteers. Focusing on the MTL, we observed that activation was significantly decreased in patients with Alzheimer's disease compared with control volunteers in the left hippocampus and parahippocampal gyrus bilaterally during the first encoding task but not during the second (P < .05, uncorrected). CONCLUSION: Functional MR imaging with a learning task seems feasible in elderly volunteers and in patients with Alzheimer's disease. The measured functional signal decrease in MTL areas warrants further exploration of the (early) diagnostic usefulness of functional MR imaging in cases of Alzheimer's disease and other dementias.

Aged↗