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Results for “Dorsolateral Prefrontal Cortex”

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PubMed2002

An auditory domain in primate prefrontal cortex.

Although neuroimaging studies confirm the frontal lobe's involvement in language processes and auditory working memory, the cellular and network basis of these functions is unclear. Physiological studies of the frontal lobe in non-human primates have focused on visual working memory and auditory spatial processing in dorsolateral prefrontal cortex (PFC), although the candidate PFC areas for non-spatial acoustic processing lie in the ventrolateral PFC (areas 12 and 45), which receives afferents from physiologically and anatomically defined auditory cortex. We recorded neuronal responses from ventrolateral PFC to auditory cues in awake monkeys under controlled conditions and report that the macaque ventrolateral PFC contains an auditory responsive domain in which neurons show responses to complex sounds, including animal and human vocalizations.

Acoustic Stimulation↗

PubMed2003

Anatomy of an error: ERP and fMRI.

Successful inhibition of pre-potent responses involves conflict; failed inhibition involves both conflict and errors, complicating the study of errors. Event-related potential (ERP) and functional magnetic resonance imaging (fMRI) data were collected while ten subjects (26-55 years old) performed a Go/NoGo task, with pre-potent responses (88% Go) and inhibition of responses (12% NoGo). We measured error-related negativity (ERN) to false alarms (FA), correct-related negativity (CRN) to hits, NoGo N2 to correct rejections (CR) and Go N2 to hits. ERP difference scores were derived (ERN-CRN; NoGoN2-GoN2) for correlating with fMRI contrasts (FA-hits; CR-hits). Age effects were removed from ERN and N2 difference scores, and conflict effects, reflected in N2 difference scores, were removed from ERN. The resulting ERN correlated with fMRI activations in both caudal and rostral anterior cingulate cortex (ACC), while N2 correlated with fMRI activations in caudal ACC and in executive control regions including dorsolateral prefrontal cortex. Thus, error and conflict monitoring may be dissociable, subserved by both overlapping and distinct ACC regions.

Adult↗

PubMed2001

Motor imagery in normal subjects and Parkinson's disease patients: an H215O PET study.

Motor imagery paradigms can be used to investigate motor preparation. We used positron emission tomography to compare regional cerebral blood flow (rCBF) in patients with Parkinson's disease and normal controls under three conditions: rest, motor imagery and motor execution. In controls, imagery activated bilateral dorsolateral and mesial frontal cortex, inferior parietal cortex and precuneus. Motor execution additionally activated primary motor cortex (p < 0.001). Between-group, for imagery there was relative reduction in dorsolateral and mesial frontal activation in the patient group (p<0.01). For execution, there was impaired activation of right dorsolateral frontal cortex and basal ganglia (p<0.01). Our results support the notion that underfunctioning of mesial frontal and dorsolateral prefrontal cortex may underlie motor preparation in Parkinson's disease but also suggest that akinesia may occur in the absence of impaired mesial frontal cortex activation.

Aged↗

PubMed1991

Selective and divided attention during visual discriminations of shape, color, and speed: functional anatomy by positron emission tomography.

Positron emission tomography (PET) was used to identify the neural systems involved in discriminating the shape, color, and speed of a visual stimulus under conditions of selective and divided attention. Psychophysical evidence indicated that the sensitivity for discriminating subtle stimulus changes in a same-different matching task was higher when subjects selectively attended to one attribute than when they divided attention among the attributes. PET measurements of brain activity indicated that modulations of extrastriate visual activity were primarily produced by task conditions of selective attention. Attention to speed activated a region in the left inferior parietal lobule. Attention to color activated a region in the collateral sulcus and dorsolateral occipital cortex, while attention to shape activated collateral sulcus (similarly to color), fusiform and parahippocampal gyri, and temporal cortex along the superior temporal sulcus. Outside the visual system, selective and divided attention activated nonoverlapping sets of brain regions. Selective conditions activated globus pallidus, caudate nucleus, lateral orbitofrontal cortex, posterior thalamus/colliculus, and insular-premotor regions, while the divided condition activated the anterior cingulate and dorsolateral prefrontal cortex. The results in the visual system demonstrate that selective attention to different features modulates activity in distinct regions of extrastriate cortex that appear to be specialized for processing the selected feature. The disjoint pattern of activations in extravisual brain regions during selective- and divided-attention conditions also suggests that preceptual judgements involve different neural systems, depending on attentional strategies.

Adult↗

PubMed2002

Functional neuroanatomy of sustained attention in schizophrenia: contribution of parietal cortices.

Deficits in sustained attention have been frequently described in schizophrenia. The neuroanatomical basis reported previously have included altered levels of activation in cingulate and prefrontal cortex, but the contribution of further regions remains unclear. We explored the full neuroanatomy underlying the sustained attentional deficits observed in naïve schizophrenics compared with controls. Participants included 10 controls and 11 patients. The experimental design included rest, auditory stimulation using clicks, and two counting tasks. Subjects were instructed to mentally count the clicks, and then to count forward at the same frequency they heard previously when listening to the clicks. Relative cerebral blood flow (relCBF) was measured by means of PET (15)O-water. Differences were observed between both groups at superior temporal cortex, superior parietal gyrus, and cerebellum during tasks requiring listening. During all counting conditions, additionally to supplementary motor area (SMA), dorsolateral prefrontal cortex (DLPCF), precentral gyrus, cingulate, cerebellum, and inferior parietal (IP) gyrus, patients engaged other frontal structures including inferior, medial, and superior frontal areas. When counting with no auditory stimulation (C; requires components of working memory and time estimation), significant differences were observed in the level of activation of frontal and IP regions. Our naïve patients presented abnormal activation of auditory associative pathways. They failed to activate prefrontal and parietal regions at a similar level during tasks requiring increased cognitive effort, and they required a higher activation of inferior frontal regions to properly respond to cognitive demands.

Adult↗

PubMed2002

Dissociation in human prefrontal cortex of affective influences on working memory-related activity.

Although neural activity associated with emotion is becoming better understood, the influence of affective parameters on brain activity reflecting cognitive functioning in humans remains poorly characterized. We examined affective influences on working memory (WM) and tested the hypotheses that (i) dorsolateral prefrontal cortex (DLPFC) activity reflecting WM is influenced by the emotion-evoking qualities of task-relevant stimuli, but only when brought "on-line" by task demands, and (ii) DLPFC and orbitofrontal cortex (OFC) activities are inversely related as a function of emotional valence. Participants performed two tasks while event-related functional MRI measured brain activity; one task required active maintenance of stimulus representations in WM, and the other task required target detection responses with no demand for WM. Stimuli were standardized emotional (pleasant and unpleasant) and neutral pictures. Emotional stimuli differentially influenced DPFC and OFC activity during WM; DLPFC was influenced by emotional valence, enhanced by pleasant and reduced by unpleasant, compared to neutral stimuli, only when task conditions required WM. OFC was valence-sensitive during both tasks, greater to arousing than neutral stimuli when WM demand was low and in inverse relationship to DLPFC with high WM demand. Further, DLPFC and OFC activities are inversely related with respect to emotional valence during the WM task. The results are consistent with the hypothesis that the intrinsic valence of task-relevant stimuli maintained in WM modulates DLPFC activity but only when the DLPFC is required for task demands. Findings suggest a conceptualization of DLPFC and its involvement in WM that takes into account a role for affective parameters.

Adult↗

PubMed2000

Synaptic mechanisms and network dynamics underlying spatial working memory in a cortical network model.

Single-neuron recordings from behaving primates have established a link between working memory processes and information-specific neuronal persistent activity in the prefrontal cortex. Using a network model endowed with a columnar architecture and based on the physiological properties of cortical neurons and synapses, we have examined the synaptic mechanisms of selective persistent activity underlying spatial working memory in the prefrontal cortex. Our model reproduces the phenomenology of the oculomotor delayed-response experiment of Funahashi et al. (S. Funahashi, C.J. Bruce and P.S. Goldman-Rakic, Mnemonic coding of visual space in the monkey's dorsolateral prefrontal cortex. J Neurophysiol 61:331-349, 1989). To observe stable spontaneous and persistent activity, we find that recurrent synaptic excitation should be primarily mediated by NMDA receptors, and that overall recurrent synaptic interactions should be dominated by inhibition. Isodirectional tuning of adjacent pyramidal cells and interneurons can be accounted for by a structured pyramid-to-interneuron connectivity. Robust memory storage against random drift of the tuned persistent activity and against distractors (intervening stimuli during the delay period) may be enhanced by neuromodulation of recurrent synapses. Experimentally testable predictions concerning the neural basis of working memory are discussed.

Animals↗

PubMed2004

Proton magnetic resonance spectroscopy in anorexia nervosa: correlations with cognition.

The aim of this study was to investigate the relationship between cognitive impairment and cerebral metabolites in patients with anorexia nervosa (AN). N-acetylaspartate (NAA), creatine/phosphocreatine (Cr), choline-containing compounds, glutamate/glutamine (Glx) and myoinositol were measured by proton magnetic resonance spectroscopy (H-MRS) of the left prefrontal cortex. Compared with healthy controls, AN patients displayed a significantly poorer performance in verbal learning and in attentional and executive tasks. Performance in the divided attention task was correlated with NAA and Cr in the dorsolateral prefrontal cortex, while executive functioning and depressive symptomatology were associated with Glx levels in the anterior cingulate. Our results provide evidence for cognitive impairment in AN patients which is associated with cerebral metabolism in the prefrontal cortex.

Adult↗

PubMed1995

Lateralization of prefrontal activation during internal mental calculation: a functional magnetic resonance imaging study.

1. Functional magnetic resonance imaging (fMRI) at 1.5 T was used to investigate the lateralization of prefrontal cortex activity during internal mental calculation in 16 human volunteers (8 right-handed and 8 left-handed). Subjects were asked to perform two different tasks: 1) a serial subtraction of prime numbers and 2) a control task in which they mentally recited numbers. 2. Signal modifications were regularly observed in the prefrontal cortex (Brodmann's area 46) during the serial subtraction of prime numbers, whereas the number listing task poorly activated the same areas. 3. In right-handed subjects, activation was clearly lateralized in the left dorsolateral prefrontal cortex, whereas a frequent bilateral activation was found in left-handed subjects. 4. We conclude that prefrontal activation during mental calculation is lateralized in a manner similar to that reported during linguistic tasks, i.e., a clear lateralization in right- but not in left-handed subjects.

Adult↗

PubMed1994

Lesions of frontal cortex diminish the auditory mismatch negativity.

Event-related brain potentials to non-attended auditory stimuli were recorded from patients with dorsolateral prefrontal cortex (DPFCx) lesions and from age-matched control subjects as they performed a visual reaction time task. Auditory stimuli consisted of monaural sequences of repetitive standard tones (1000 Hz) and occasional deviant tones of a higher frequency (1300 Hz). In comparison with control subjects, DPFCx patients showed enhanced P1 amplitudes (mean peak latency 50 msec), consistent with reduced frontally mediated gating of sensory input to the auditory cortex. The mismatch negativity (MMN) elicited by deviant tones was reduced in DPFCx patients over a broad latency range (130-210 msec), especially over the lesioned hemisphere and for tones delivered to the ear ipsilateral to the lesion. The results suggest that DPFCx and DPFCx-temporal projections play a critical role in involuntary orienting to physical changes in sequences of non-attended auditory stimuli.

Acoustic Stimulation↗

PubMed2003

Changes in emotion after circumscribed surgical lesions of the orbitofrontal and cingulate cortices.

To analyse the functions of different parts of the prefrontal cortex in emotion, patients with different prefrontal surgical excisions were compared on four measures of emotion: voice and face emotional expression identification, social behaviour, and the subjective experience of emotion. Some patients with bilateral lesions of the orbitofrontal cortex (OFC) had deficits in voice and face expression identification, and the group had impairments in social behaviour and significant changes in their subjective emotional state. Some patients with unilateral damage restricted to the OFC also had deficits in voice expression identification, and the group did not have significant changes in social behaviour or in their subjective emotional state. Patients with unilateral lesions of the antero-ventral part of the anterior cingulate cortex (ACC) and/or medial Brodmann area (BA) 9 were, in some cases, impaired on voice and face expression identification, had some change in social behaviour, and had significant changes in their subjective emotional state. Patients with unilateral lesions of the OFC and of the ACC and/or medial BA 9 were, in some cases, impaired on voice and face expression identification, had some changes in social behaviour, and had significant changes in their subjective emotional state. Patients with dorsolateral prefrontal cortex lesions or with medial lesions outside ACC and medial BA 9 areas (dorsolateral/other medial group) were unimpaired on any of these measures of emotion. In all cases in which voice expression identification was impaired, there were no deficits in control tests of the discrimination of unfamiliar voices and the recognition of environmental sounds. Thus bilateral or unilateral lesions circumscribed surgically within the OFC can impair emotional voice and/or face expression identification, but significant changes in social behaviour and in subjective emotional state are related to bilateral lesions. Importantly, unilateral lesions of the ACC (including some of medial BA 9) can produce voice and/or face expression identification deficits, and marked changes in subjective emotional state. These findings with surgically circumscribed lesions show that within the prefrontal cortex, both the OFC and the ACC/medial BA 9 region are involved in a number of aspects of emotion in humans including emotion identification, social behaviour and subjective emotional state, and that the dorsolateral prefrontal areas are not involved in emotion in these ways.

Adult↗

PubMed1991

Language activation studies with positron emission tomography.

Behavioural tasks produce changes in regional cerebral blood flow (rCBF), the result of increased local neural activity. These changes can be measured with positron emission tomography (PET). Language activation studies by means of PET are being used to relate regional patterns of cerebral activation to information-processing models of speech and reading. Significant activation confined to both superior temporal gyri has been observed when normal subjects hear words played backwards, listen to non-words, and perform category judgements on pairs of heard real words. Prestriate cortex is activated by seeing strings of letter-like symbols, consonant strings, pronounceable non-words and real words, with additional activation in left medial prestriate cortex in response to the non-words and real words. Left posterior superior temporal gyrus (PSTG), left dorsolateral prefrontal cortex (DLPFC) and supplementary motor area (SMA) are engaged when subjects retrieve verbs from memory to match nouns. Finally, primary sensorimotor cortex is activated during articulation. There is particular interest at present in the precise roles of left PSTG and DLPFC in single-word comprehension and generation, and interpretation of the results depends critically on the design of the single-word tasks used for behavioural activation.

Aphasia↗

PubMed2006

One session of high frequency repetitive transcranial magnetic stimulation (rTMS) to the right prefrontal cortex transiently reduces cocaine craving.

BACKGROUND: Cocaine dependence is a public health problem affecting 2 million individuals in USA. Craving is a predictor of subsequent cocaine use and is related to changes in brain activity in networks involving the prefrontal cortex. METHODS: We investigated the efficacy of one session of high frequency repetitive transcranial magnetic stimulation (rTMS) to reduce craving in cocaine addicted subjects. Six patients underwent two sessions of 10Hz rTMS over left or right dorsolateral prefrontal cortex (DLPFC). Before, immediately after and 4h after rTMS we measured craving using visual analogue scales. RESULTS: Right, but not left, DLPFC stimulation significantly reduced craving over time (F(2,10)=11.07, p=0.0029). The reduction was 19% (13.4-24.6%) from baseline and disappeared after 4h. The interaction of time by site of stimulation for craving was also significant (F(2,25)=6.13, p=0.0068). CONCLUSION: One session of 10Hz rTMS over right, but not left, DLPFC transiently reduces craving in cocaine dependent individuals. These results highlight the potential of non-invasive neuromodulation as a therapeutic tool for cocaine addiction.

Adult↗

PubMed2004

Movement preparation in self-initiated versus externally triggered movements: an event-related fMRI-study.

In the present study, we used fMRI to investigate whether event-related preparatory processes of self-initiated and externally triggered movements differ. Twenty subjects were examined with 1000 T2*-weighted images in two consecutive sessions. During the first session subjects performed self-initiated abductions of the right index finger. For the second session subjects were instructed to perform the movements in response to visual cues. Number and timing of movements were matched between conditions. For statistical inference on multisubject level, random effects analyses were performed. Significantly enhanced activity during self-initiated compared to externally triggered movements was found within the left SMA, the left pre- and sensorimotor cortex, the right putamen, the left anterior cingulate gyrus, and the left inferior parietal lobe. The significantly increased activity during self-initiated in comparison to externally triggered movements might represent differential demands of the two conditions on the neuronal motor net during movement preparation, reflecting utilization of precise knowledge when to move in self-initiated movements. Our results emphasize a possible role of the primary motor cortex for movement preparation as observed in electrophysiological studies, but do not support a specific involvement of the dorsolateral prefrontal cortex as suggested by former block design studies.

Adult↗

PubMed2005

The neural bases of amusement and sadness: a comparison of block contrast and subject-specific emotion intensity regression approaches.

Neuroimaging studies have made substantial progress in elucidating the neural bases of emotion. However, few studies to date have directly addressed the subject-specific, time-varying nature of emotional responding. In the present study, we employed functional magnetic resonance imaging to examine the neural bases of two common emotions--amusement and sadness--using both (a) a stimulus-based block contrast approach and (b) a subject-specific regression analysis using continuous ratings of emotional intensity. Thirteen women viewed a set of nine 2-min amusing, sad, or neutral film clips two times. During the first viewing, participants watched the film stimuli. During the second viewing, they made continuous ratings of the intensity of their own amusement and sadness during the first film viewing. For sad films, both block contrast and subject-specific regression approaches resulted in activations in medial prefrontal cortex, inferior frontal gyrus, superior temporal gyrus, precuneus, lingual gyrus, amygdala, and thalamus. For amusing films, the subject-specific regression analysis demonstrated significant activations not detected by the block contrast in medial, inferior frontal gyrus, dorsolateral prefrontal cortex, posterior cingulate, temporal lobes, hippocampus, thalamus, and caudate. These results suggest a relationship between emotion-specific temporal dynamics and the sensitivity of different data analytic methods for identifying emotion-related neural responses. These findings shed light on the neural bases of amusement and sadness, and highlight the value of using emotional film stimuli and subject-specific continuous emotion ratings to characterize the dynamic, time-varying components of emotional responses.

Adult↗

PubMed2000

Nicotine impairs spatial working memory while leaving spatial attention intact.

We investigated the effects of nicotine on spatial working memory and spatial selective attention in young, healthy smokers. Spatial working memory was assessed by a delayed response task. Delayed response performance is associated with the integrity of the dorsolateral prefrontal cortex. Spatial interference and negative priming tasks were used to assess spatial selective attention. Nicotine impaired spatial working memory in smokers but it did not affect spatial selective attention. This result suggests that nicotine may impair dorsolateral prefrontal function, as assessed by the spatial working memory task in young smokers and that this deficit does not stem from impairments in spatial selective attention. However, the effects of nicotine on working memory and selective attention in nonsmokers or in psychiatric population with suspected nicotinic receptor abnormalities (e.g., schizophrenia patients) cannot be deduced from the present study.

Adult↗

PubMed2004

Functional MRI neuroanatomic correlates of the Hooper Visual Organization Test.

The Hooper Visual Organization Test (VOT), a commonly applied neuropsychological test of visual spatial ability, is used for assessing patients with suspected right hemisphere, or parietal lobe involvement. A controversy has developed over whether the inferences of this test metric can be assumed to involve global, lateralized, or regional functionality. In this study, the characteristic visual organization and object naming aspects of the VOT task presentation were adapted to a functional MR imaging (fMRI) paradigm to probe the neuroanatomic correlates of this neuropsychological test. Whole brain fMRI mapping results are reported on a cohort of normal subjects. Bilateral fMRI responses were found predominantly in the posterior brain, in regions of superior parietal lobules, ventral temporal-occipital cortex, and posterior visual association areas, and to a lesser extent, the frontal eye fields bilaterally, and left dorsolateral prefrontal cortex. The results indicate a general brain region or network in which VOT impairment, due to its visuospatial and object identification demands, is possible to be detected. Discussion is made of interpretive limitations when adapting neuropsychological tests to fMRI analysis.

Adult↗

PubMed2000

Cortical processing of human somatic and visceral sensation.

Somatic sensation can be localized precisely, whereas localization of visceral sensation is vague, possibly reflecting differences in the pattern of somatic and visceral input to the cerebral cortex. We used functional magnetic resonance imaging to study the cortical processing of sensation arising from the proximal (somatic) and distal (visceral) esophagus in six healthy male subjects. Esophageal stimulation was performed by phasic distension of a 2 cm balloon at 0.5 Hz. For each esophageal region, five separate 30 sec periods of nonpainful distension were alternated with five periods of similar duration without distension. Gradient echoplanar images depicting bold contrast were acquired using a 1.5 T GE scanner. Distension of the proximal esophagus was localized precisely to the upper chest and was represented in the trunk region of the left primary somatosensory cortex. In contrast, distension of the distal esophagus was perceived diffusely over the lower chest and was represented bilaterally at the junction of the primary and secondary somatosensory cortices. Different activation patterns were also observed in the anterior cingulate gyrus with the proximal esophagus being represented in the right midanterior cingulate cortex (BA 24) and the distal esophagus in the perigenual area (BA32). Differences in the activation of the dorsolateral prefrontal cortex and cerebellum were also observed for the two esophageal regions. These findings suggest that cortical specialization in the sensory-discriminative, affective, and cognitive areas of the cortex accounts for the perceptual differences observed between the two sensory modalities.

Adult↗