7 results
Response-related fMRI of veridical and false recognition of words
- Reinhard Heun, Frank Jessen, Uwe Klose, Michael Erb, Dirk-Oliver Granath, Wolfgang Grodd
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- Journal:
- European Psychiatry / Volume 19 / Issue 1 / January 2004
- Published online by Cambridge University Press:
- 16 April 2020, pp. 42-52
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Objectives. – Studies on the relation between local cerebral activation and retrieval success usually compared high and low performance conditions, and thus showed performance-related activation of different brain areas. Only a few studies directly compared signal intensities of different response categories during retrieval. During verbal recognition, we recently observed increased parieto-occipital activation related to false alarms. The present study intends to replicate and extend this observation by investigating common and differential activation by veridical and false recognition.
Methods. – Fifteen healthy volunteers performed a verbal recognition paradigm using 160 learned target and 160 new distracter words. The subjects had to indicate whether they had learned the word before or not. Echo-planar MRI of blood-oxygen-level-dependent signal changes was performed during this recognition task. Words were classified post hoc according to the subjects’ responses, i.e. hits, false alarms, correct rejections and misses. Response-related fMRI-analysis was used to compare activation associated with the subjects’ recognition success, i.e. signal intensities related to the presentation of words were compared by the above-mentioned four response types.
Results. – During recognition, all word categories showed increased bilateral activation of the inferior frontal gyrus, the inferior temporal gyrus, the occipital lobe and the brainstem in comparison with the control condition. Hits and false alarms activated several areas including the left medial and lateral parieto-occipital cortex in comparison with subjectively unknown items, i.e. correct rejections and misses. Hits showed more pronounced activation in the medial, false alarms in the lateral parts of the left parieto-occipital cortex.
Conclusions. – Veridical and false recognition show common as well as different areas of cerebral activation in the left parieto-occipital lobe: increased activation of the medial parietal cortex by hits may correspond to true recognition, increased activation of the parieto-occipital cortex by false alarms may correspond to familiarity decisions. Further studies are needed to investigate the reasons for false decisions in healthy subjects and patients with memory problems.
Loneliness and depression dissociated on parietal-centered networks in cognitive and resting states
- Robin Shao, Ho-Ling Liu, Chih-Mao Huang, Yao-Liang Chen, Mengxia Gao, Shwu-Hua Lee, Chemin Lin, Tatia M. C. Lee
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- Journal:
- Psychological Medicine / Volume 50 / Issue 16 / December 2020
- Published online by Cambridge University Press:
- 16 October 2019, pp. 2691-2701
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Background
Perceived loneliness, an increasingly prevalent social issue, is closely associated with major depressive disorder (MDD). However, the neural mechanisms previously implicated in key cognitive and affective processes in loneliness and MDD still remain unclear. Such understanding is critical for delineating the psychobiological basis of the relationship between loneliness and MDD.
MethodsWe isolated the unique and interactive cognitive and neural substrates of loneliness and MDD among 27 MDD patients (mean age = 51.85 years, 20 females), and 25 matched healthy controls (HCs; mean age = 48.72 years, 19 females). We assessed participants' behavioral performance and neural regional and network functions on a Stroop color-word task, and their resting-state neural connectivity.
ResultsBehaviorally, we found greater incongruence-related accuracy cost in MDD patients, but reduced incongruence effect on reaction time in lonelier individuals. When performing the Stroop task, loneliness positively predicted prefrontal-anterior cingulate-parietal connectivity across all participants, whereas MDD patients showed a decrease in connectivity compared to controls. Furthermore, loneliness negatively predicted parietal and cerebellar activities in MDD patients, but positively predicted the same activities in HCs. During resting state, MDD patients showed reduced parietal-anterior cingulate connectivity, which again positively correlated with loneliness in this group.
ConclusionsWe speculate the distinct neurocognitive profile of loneliness might indicate increase in both bottom-up attention and top-down executive control functions. However, the upregulated cognitive control processes in lonely individuals may eventually become exhausted, which may in turn predispose to MDD onset.
Motor Adaptation Deficits in Ideomotor Apraxia
- Pratik K. Mutha, Lee H. Stapp, Robert L. Sainburg, Kathleen Y. Haaland
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- Journal:
- Journal of the International Neuropsychological Society / Volume 23 / Issue 2 / February 2017
- Published online by Cambridge University Press:
- 16 February 2017, pp. 139-149
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Objectives: The cardinal motor deficits seen in ideomotor limb apraxia are thought to arise from damage to internal representations for actions developed through learning and experience. However, whether apraxic patients learn to develop new representations with training is not well understood. We studied the capacity of apraxic patients for motor adaptation, a process associated with the development of a new internal representation of the relationship between movements and their sensory effects. Methods: Thirteen healthy adults and 23 patients with left hemisphere stroke (12 apraxic, 11 nonapraxic) adapted to a 30-degree visuomotor rotation. Results: While healthy and nonapraxic participants successfully adapted, apraxics did not. Rather, they showed a rapid decrease in error early but no further improvement thereafter, suggesting a deficit in the slow, but not the fast component of a dual-process model of adaptation. The magnitude of this late learning deficit was predicted by the degree of apraxia, and was correlated with the volume of damage in parietal cortex. Apraxics also demonstrated an initial after-effect similar to the other groups likely reflecting the early learning, but this after-effect was not sustained and performance returned to baseline levels more rapidly, consistent with a disrupted slow learning process. Conclusions: These findings suggest that the early phase of learning may be intact in apraxia, but this leads to the development of a fragile representation that is rapidly forgotten. The association between this deficit and left parietal damage points to a key role for this region in learning to form stable internal representations. (JINS, 2017, 23, 139–149)
White-matter abnormalities in the right posterior hemisphere in generalized anxiety disorder: a diffusion imaging study
- P. Brambilla, G. Como, M. Isola, F. Taboga, R. Zuliani, S. Goljevscek, M. Ragogna, G. Brondani, M. Baiano, L. Perini, A. Ferro, M. Bazzocchi, C. Zuiani, M. Balestrieri
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- Journal:
- Psychological Medicine / Volume 42 / Issue 2 / February 2012
- Published online by Cambridge University Press:
- 25 July 2011, pp. 427-434
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Background
Prior imaging studies have shown structural, functional and biochemical impairments in patients with generalized anxiety disorder (GAD), particularly in the right hemisphere. In this study we investigated, for the first time to the best of our knowledge, the white-matter microstructure organization in GAD.
MethodA total of 12 patients with DSM-IV GAD and 15 matched healthy controls underwent a magnetic resonance imaging session of diffusion weighted imaging, exploring white-matter water molecules by the means of apparent diffusion coefficients (ADCs). Regions of interests were placed in the frontal, parietal, temporal and occipital lobes and in the splenium and genu of the corpus callosum, bilaterally.
ResultsADC measures were significantly greater in patients with GAD in the right splenium and right parietal cortex compared with healthy controls (p⩽0.002). No significant correlations between ADCs and age or clinical variables were found.
ConclusionsWe provide evidence that GAD is associated with disrupted white-matter coherence of posterior right hemisphere regions, which may partly sustain the impaired cognitive regulation of anxiety. Future diffusion imaging investigations are expected to better elucidate the communication between the parietal cortex and other right hemisphere regions in sustaining the cognitive processing of social and emotional stimuli in patients with GAD.
Gaze field properties of eye position neurones in areas MST and 7a of the macaque monkey
- S. Squatrito, M. G. Maioli
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- Journal:
- Visual Neuroscience / Volume 13 / Issue 2 / March 1996
- Published online by Cambridge University Press:
- 02 June 2009, pp. 385-398
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The activity of parietal cortex neurones primarily related to eye position (EP neurones) was studied in macaque monkeys with the aim of precisely defining the neurones' gaze fields (GF) and comparing them in two functionally different areas, MSTd and 7a. Discharge rates of single neurones in the inferior parietal lobule and in the underlying cortex of the superior temporal sulcus were recorded in two Java monkeys while the animals fixated a steady visual target positioned at several different points on a video screen. The GFs were then drawn as a regression surface fitting the mean discharge rates. Cells tonically influenced by the angle of gaze were found in both areas. The GFs most often took the form of a nearly planar surface best characterized as a ramp tilted towards a hemifield or quadrant of the visual field, shifted eccentrically with respect to the straight ahead (primary position), and with a midpoint centred between 0 deg and 20 deg of gaze eccentricity and saturation between 10 deg and 35 deg. In a minority of cases, the discharge rate was nearly maximal at the primary position and decreased to a minimum within 35 deg of eccentricity. In other instances, the GFs were peaked surfaces, limited to a restricted part of visual space. EP neurones, while showing similar gaze fields in areas MST and 7a, were found intermingled with functionally different types of cells. The results suggest that EP neurones similar to those already described in several areas of the monkey parietal cortex are present also in area MST. These cells, by signalling the degree of gaze eccentricity from the primary position, encode gaze position in an orbito-centered frame extending up to 30–35 deg from the straight-ahead. The role of EP neurones might be to supply contiguous elements with a gaze eccentricity signal required for visuo-motor processes such as the control of tracking movements.
Single neurons with both form/color differential responses and saccade-related responses in the nonretinotopic pulvinar of the behaving macaque monkey
- Louis A. Benevento, John D. Port
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- Journal:
- Visual Neuroscience / Volume 12 / Issue 3 / May 1995
- Published online by Cambridge University Press:
- 02 June 2009, pp. 523-544
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The nonretinotopic portion of the macaque pulvinar complex is interconnected with the occipitoparietal and occipitotemporal transcortical visual systems where information about the location and motion of a visual object or its form and color are modulated by eye movements and attention. We recorded from single cells in and about the border of the dorsal portion of the lateral pulvinar and the adjacent medial pulvinar of awake behaving Macaca mulatta in order to determine how the properties of these two functionally dichotomous cortical systems were represented. We found a class of pulvinar neurons that responded differentially to ten different patterns or broadband wavelengths (colors). Thirty-four percent of cells tested responded to the presentation of at least one of the pattern or color stimuli. These cells often discharged to several of the patterns or colors, but responded best to only one or two of them, and 86% were found to have statistically significant pattern and/or color preferences. Pattern/color preferential cells had an average latency of 79.1 ± 46.0 ms (range 31–186 ms), responding well before most inferotemporal cortical cell responses. Visually guided and memory-guided saccade tasks showed that 58% of pattern/color preferential cells also had saccade-related properties e.g. directional presaccadic and postsaccadic discharges, and inhibition of activity during the saccade. In the pulvinar, the mean presaccadic response latency was earlier, and the mean postsaccadic response latency was later, than those reported for parietal cortex. We also discovered that the strength of response to patterns or colors changed depending upon the behavioral setting. In comparison to trials in which the monkey fixated dead ahead during passive presentations of pattern and color stimuli, 92% of the cells showed attenuated responses to the same passive presentation of patterns and colors during fixation when these trials were interleaved with trials which also required active saccades to pattern and color targets in the periphery. We conclude that properties which represent the functionally dichotomous object and spatial visual systems are found together in single pulvinar neurons and that the responses of these cells to pattern or color stimuli are influenced by the focus of spatial attention. The pulvinar is the first structure in the brain shown to have neurons which integrate both object and spatial properties and the response latencies indicate that this information is processed before that in cortex. These results are discussed in terms of role of the pulvinar in visual attention as well as its unique role in providing both object feature and spatial location information to the inferotemporal cortex.
Temporal properties of optic flow responses in the ventral intraparietal area
- S.F. GABEL, H. MISSLISCH, S.J. SCHAAFSMA, J. DUYSENS
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- Journal:
- Visual Neuroscience / Volume 19 / Issue 3 / May 2002
- Published online by Cambridge University Press:
- 05 September 2002, pp. 381-388
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The ventral intraparietal area (VIP) is located at the end of the dorsal stream. Its neurons are known to have receptive-field characteristics similar to those of MT and MST neurons, but little is known about the temporal characteristics of VIP cells' responses. How fast are directionally selective responses evoked in the ventral intraparietal area after viewing optic flow patterns, and what are the temporal properties of these neuronal responses? To examine these questions, we recorded the activity of 37 directionally selective ventral intraparietal area (VIP) neurons in two awake macaque monkeys in response to optic flow stimuli with presentation times ranging from 17 ms to 2000 ms. We found a minimum response latency of 45 ms, and a median latency of 152 ms. Of all neurons, 10% showed early response components only (response latency < 150 ms and no activity in 500–2000 ms interval after stimulus onset), 55% only late response components (response latency >150 ms and sustained activity in 500–2000 ms interval), and 35% both early and late response components. Early responses appeared to very brief stimulus presentations (33-ms duration), while the late responses required longer stimulus durations. The directional selectivity was independent of optic flow duration in all cells. These results suggest that only a subset of neurons in area VIP may contribute to the fast processing of optic flow, while showing that the temporal properties of VIP responses clearly differ from the temporal characteristics of neurons in areas MT and MST.