Cerebral Activation Patterns Research Articles

242 Brain Processing of Rectal Sensation in Children With Chronic Functional Constipation

Background and Objective: The pathophysiology underlying pediatric chronic functional constipation (FC) is poorly understood. These children often report loss of sensation of urge to defecate. Functional magnetic resonance imaging (fMRI) studies have been used to unravel brain processing of visceral sensation in adults with functional gastrointestinal disorders. However, brain-imaging data are lacking in both adults and children with constipation. The aim is to investigate the cerebral activity in response to rectal distension in children with FC and in healthy controls (HCs). Methods: 15 patients with FC (8M/7F; mean age 14.3 yrs, range 12-18 yrs) and 15 HCs (6M/9F; mean age 20.1 yrs, range 18-21 yrs) participated. Rectal barostat was performed prior to the fMRI scan. A stepwise pressure-controlled distension protocol was used to determine the pressure threshold for urge sensation. Subjects received 2 sessions of 5 stimulations consisting of repetitions of 30 sec of rectal stimulation with previous defined pressure threshold, followed by 30 sec of rest during acquisition blood oxygenation level-dependent (BOLD) fMRI. Images were acquired on a 3Tesla MRI scanner with an 8-channel SENSE head receive coil. A T2*-weighted echo planar imaging sequence was acquired with: TR/TE=3000/30 ms, slice thickness=3.0 mm, voxel size=1.72 x 1.72 x 3 mm, with 40 axial slices, in ascending mode covering the whole brain. fMRI signal differences were analyzed using SPM8 in Matlab, thresholded at p<0.001. Cerebral activation was defined as BOLD increase during rectal distension and cerebral deactivation as BOLD decrease during rectal distension. Results: FC patients had higher thresholds for urgency than HCs (p<0.001). FC patients needed a mean pressure of 18.2 mmHg above MDP to provoke urge sensation, compared to a mean pressure of 8.6 mmHg above MDP in HCs. The groups were differentiated by both activated and deactivated regions in response to rectal distension. FC patients showed activation in the dorsolateral prefrontal cortex and deactivation in the median somatosensory cortex, insula and amygdala. HCs showed deactivation in the same areas, but in contrast, no regions showed significant activation in response to rectal distension. Conclusion: This is the first study evaluating cerebral processing of rectal sensation in constipated patients. FC patients and HCs had a different pattern of cerebral activation and deactivation during rectal distension, suggesting different neural processing of rectal urge sensation in brain regions previously implicated in adult studies using visceral pain stimuli.

Abstract T P364: Longitudinal Evaluation of Functional Magnetic Resonance Imaging on Working Memory in Patients after Transient Ischemic Attack

OBJECTIVE: Transient ischemic attack (TIA) can increase the risk of cognitive decline, especially in attention-executive-psychomotor functioning. However, whether TIA patients have altered patterns of brain activation during this function, and whether there is a dynamic change on cerebral activity patterns, have not been examined to date. This study is designed to using functional magnetic resonance imaging (fMRI) to investigate longitudinal changes in brain activation during a verbal working memory (VWM) task in patients with TIA. METHODS: The current study included 25 patients with first-ever TIA in right hemisphere and 25 healthy volunteers. N-Back VWM task-related fMRI were conducted one week and three months after TIA onset. The brain activity evoked by n-back task in the patients was assessed and compared with that of the controls. Significant changes in cerebral activation over time were also observed in TIA patients. RESULTS: The groups did not differ on any demographic, cognitive and task performance variables. Compared with healthy subjects, patients at one week after TIA demonstrated increased activity in bilateral inferior frontal gyrus (IFG), right dorsolateral prefrontal cortex (DLPFC), insula, inferior parietal lobe (IPL) and cerebellum during the task. However, at 3-month follow-up, the task-related brain activity in patients was clearly less recruited, and only right IFG still exhibited increased activity. Moreover, a direct comparison of fMRI data between one week and three months after TIA showed that there was increased activation in bilateral middle temporal gyrus (MTG), right DLPFC, IPL, cerebellum and left IFG in patients at one week after TIA. CONCLUSIONS: These findings support the hypotheses that the patterns of brain activity during VWM performance may change for a period of time post-TIA despite the cessation of clinical symptoms. They also provide evidence of a progressive normalization of the VWM activation pattern after transient episodes of ischemia in patients with first-ever TIA.

Functional neuroimaging of conversion disorder: the role of ancillary activation.

BackgroundPrevious functional neuroimaging studies investigating the neuroanatomy of conversion disorder have yielded inconsistent results that may be attributed to small sample sizes and disparate methodologies. The objective of this study was to better define the functional neuroanatomical correlates of conversion disorder.MethodsTen subjects meeting clinical criteria for unilateral sensory conversion disorder underwent fMRI during which a vibrotactile stimulus was applied to anesthetic and sensate areas. A block design was used with 4 s of stimulation followed by 26 s of rest, the pattern repeated 10 times. Event-related group averages of the BOLD response were compared between conditions.ResultsAll subjects were right-handed females, with a mean age of 41. Group analyses revealed 10 areas that had significantly greater activation (p < .05) when stimulation was applied to the anesthetic body part compared to the contralateral sensate mirror region. They included right paralimbic cortices (anterior cingulate cortex and insula), right temporoparietal junction (angular gyrus and inferior parietal lobule), bilateral dorsolateral prefrontal cortex (middle frontal gyri), right orbital frontal cortex (superior frontal gyrus), right caudate, right ventral-anterior thalamus and left angular gyrus. There was a trend for activation of the somatosensory cortex contralateral to the anesthetic region to be decreased relative to the sensate side.ConclusionsSensory conversion symptoms are associated with a pattern of abnormal cerebral activation comprising neural networks implicated in emotional processing and sensory integration. Further study of the roles and potential interplay of these networks may provide a basis for an underlying psychobiological mechanism of conversion disorder.

Individuals Diagnosed with Schizophrenia Assign Emotional Importance to Neutral Stimuli: An fMRI Study

The majority of functional neuroimaging studies investigating neural correlates of emotion processing in schizophrenia report a significant deficit in limbic structures activation in patients relative to control participants. Recently it has been suggested that this apparent “deficit” could be due to an enhanced sensitivity of the neutral material in individuals diagnosed with schizophrenia, rather than due to their inefficiency in emotion processing. The purpose of the present study was to test this supposition and verify if the potential effect is present in both men and women diagnosed with schizophrenia. In order to do that we examined the pattern of cerebral activation associated with processing of neutral stimuli in schizophrenia. Thirty-seven schizophrenia patients and 37 healthy controls viewed neutral and emotional images while in a functional magnetic resonance imaging scanner. Schizophrenia patients rated the neutral images as more emotionally salient than controls. Additionally, patients showed significant activation during processing of neutral images in limbic and prefrontal regions; similar areas were underactivated in patients relative to controls during processing of emotional information. Investigation of sex differences revealed that the enhanced responsiveness to the emotionally neutral material was attributed primarily to men with schizophrenia.

Incongruent object/context relationships in visual scenes: Where are they processed in the brain?

Rapid object visual categorization in briefly flashed natural scenes is influenced by the surrounding context. The neural correlates underlying reduced categorization performance in response to incongruent object/context associations remain unclear and were investigated in the present study using fMRI. Participants were instructed to categorize objects in briefly presented scenes (exposure duration=100ms). Half of the scenes consisted of objects pasted in an expected (congruent) context, whereas for the other half, objects were embedded in incongruent contexts. Object categorization was more accurate and faster in congruent relative to incongruent scenes. Moreover, we found that the two types of scenes elicited different patterns of cerebral activation. In particular, the processing of incongruent scenes induced increased activations in the parahippocampal cortex, as well as in the right frontal cortex. This higher activity may indicate additional neural processing of the novel (non experienced) contextual associations that were inherent to the incongruent scenes. Moreover, our results suggest that the locus of object categorization impairment due to contextual incongruence is in the right anterior parahippocampal cortex. Indeed in this region activity was correlated with the reaction time increase observed with incongruent scenes. Representations for associations between objects and their usual context of appearance might be encoded in the right anterior parahippocampal cortex.

Perceptual Restoration of Degraded Speech Is Preserved with Advancing Age

Cognitive skills, such as processing speed, memory functioning, and the ability to divide attention, are known to diminish with aging. The present study shows that, despite these changes, older adults can successfully compensate for degradations in speech perception. Critically, the older participants of this study were not pre-selected for high performance on cognitive tasks, but only screened for normal hearing. We measured the compensation for speech degradation using phonemic restoration, where intelligibility of degraded speech is enhanced using top-down repair mechanisms. Linguistic knowledge, Gestalt principles of perception, and expectations based on situational and linguistic context are used to effectively fill in the inaudible masked speech portions. A positive compensation effect was previously observed only with young normal hearing people, but not with older hearing-impaired populations, leaving the question whether the lack of compensation was due to aging or due to age-related hearing problems. Older participants in the present study showed poorer intelligibility of degraded speech than the younger group, as expected from previous reports of aging effects. However, in conditions that induce top-down restoration, a robust compensation was observed. Speech perception by the older group was enhanced, and the enhancement effect was similar to that observed with the younger group. This effect was even stronger with slowed-down speech, which gives more time for cognitive processing. Based on previous research, the likely explanations for these observations are that older adults can overcome age-related cognitive deterioration by relying on linguistic skills and vocabulary that they have accumulated over their lifetime. Alternatively, or simultaneously, they may use different cerebral activation patterns or exert more mental effort. This positive finding on top-down restoration skills by the older individuals suggests that new cognitive training methods can teach older adults to effectively use compensatory mechanisms to cope with the complex listening environments of everyday life.

Assessment of cerebral activation patterns while operating a driving simulator with TBI survivors: A functional near-infrared spectroscopy study

Assessment of cerebral activation patterns while operating a driving simulator with TBI survivors: A functional near-infrared spectroscopy study

Self-reflection and positive schizotypy in the adolescent brain

Clinical and phenomenological accounts of schizophrenia suggest that impairments in self-reflective processes significantly contribute to psychopathological expression. Recent imaging studies observe atypical cerebral activation patterns during self-reflection, especially around the cortical midline structures, both in psychosis-prone adults and individuals with schizophrenia. Given that self-reflection processes consolidate during adolescence, and that early transient expression of psychosis (positive schizotypy) also arises during this period, the present study sought to examine whether atypical cerebral activation during self-reflection task could be associated with early schizotypic expression during adolescence. Forty-two neurotypical adolescent participants (19 females) aged from 12 to 19 (15.92±1.9) underwent a self-reflection task using functional neuroimaging (fMRI), where they had to evaluate trait adjectives (1 to 4 ratings) about themselves or their same sex best friend. The Schizotypal Personality Questionnaire (SPQ) was employed to assess positive schizotypic expression. Results showed that positive schizotypy in adolescents significantly correlated with cortical midline activation patterns in the dorsomedial prefrontal cortex (dmPFC) and the posterior cingulate cortex (PCC), as well as the dorsolateral PFC and the lingual gyrus. The results are consistent with previous imaging literature on self-reflection and schizophrenia. They further highlight that the relationship between self-reflection processes and positive schizotypy operates at the trait level of expression and can be observed as early as adolescence.

Is a neutral expression also a neutral stimulus? A study with functional magnetic resonance

Although neutral faces do not initially convey an explicit emotional message, it has been found that individuals tend to assign them an affective content. Moreover, previous research has shown that affective judgments are mediated by the task they have to perform. Using functional magnetic resonance imaging in 21 healthy participants, we focus this study on the cerebral activity patterns triggered by neutral and emotional faces in two different tasks (social or gender judgments). Results obtained, using conjunction analyses, indicated that viewing both emotional and neutral faces evokes activity in several similar brain areas indicating a common neural substrate. Moreover, neutral faces specifically elicit activation of cerebellum, frontal and temporal areas, while emotional faces involve the cuneus, anterior cingulated gyrus, medial orbitofrontal cortex, posterior superior temporal gyrus, precentral/postcentral gyrus and insula. The task selected was also found to influence brain activity, in that the social task recruited frontal areas while the gender task involved the posterior cingulated, inferior parietal lobule and middle temporal gyrus to a greater extent. Specifically, in the social task viewing neutral faces was associated with longer reaction times and increased activity of left dorsolateral frontal cortex compared with viewing facial expressions of emotions. In contrast, in the same task emotional expressions distinctively activated the left amygdale. The results are discussed taking into consideration the fact that, like other facial expressions, neutral expressions are usually assigned some emotional significance. However, neutral faces evoke a greater activation of circuits probably involved in more elaborate cognitive processing.

AEEG and NIRS during transition and resuscitation after birth: Promising additional tools; an observational study

Aim of the studyDuring resuscitation no routine cerebral monitoring is available. We aimed at monitoring cerebral activity and oxygenation continuously during neonatal transition and resuscitation. MethodsNeonates ≥34 weeks of gestation born via cesarean section were included. Cerebral activity was continuously measured with amplitude-integrated-EEG (aEEG) and cerebral oxygenation (rSO2) with near-infrared-spectroscopy (NIRS) during the first 10min after birth. For quantitative analysis of aEEG every minute the mean minimum amplitude (Vmin) and maximum amplitude (Vmax) was determined. Uncompromised neonates were compared to neonates in need of resuscitation. ResultsOut of 224 eligible neonates 31 uncompromised and 15 in need of respiratory support were included. Uncompromised neonates showed higher values for Vmin in the third minute and higher values for Vmax in the third and fourth minute compared to the tenth minute post-partum. In uncompromised neonates rSO2 values during the first 6min after birth were lower compared to minute ten. Neonates in need of respiratory support had lower rSO2 values over the first 8min after birth compared to minute ten. ConclusionsThis is the first study demonstrating that monitoring of aEEG and NIRS to measure cerebral activity and oxygenation during immediate postpartum transition is feasible. During transition compromised neonates requiring resuscitation showed a different cerebral activity pattern compared to uncompromised neonates.

Effects of age on negative BOLD signal changes in the primary somatosensory cortex

In addition to a contralateral activation of the primary and secondary somatosensory cortices, peripheral sensory stimulation has been shown to elicit responses in the ipsilateral primary somatosensory cortex (SI). In particular, evidence is accumulating that processes of interhemispheric inhibition as depicted by negative blood oxygenation level dependent (BOLD) signal changes are part of somatosensory processes. The aim of the study was to analyze age-related differences in patterns of cerebral activation in the somatosensory system in general and processes of interhemispheric inhibition in particular. For this, a functional magnetic resonance imaging (fMRI) study was performed including 14 younger (mean age 23.3±0.9years) and 13 healthy older participants (mean age 73.2±8.3years). All subjects were scanned during peripheral electrical median nerve stimulation (40Hz) to obtain BOLD responses in the somatosensory system. Moreover, the individual current perception threshold (CPT) as a quantitative measure of sensory function was determined in a separate psychophysical testing. Significant increases in BOLD signal across the entire group could be measured within the contralateral SI, in the bilateral secondary somatosensory cortex (SII), the contralateral supplementary motor area and the insula. Negative BOLD signal changes were delineated in ipsilateral SI/MI as well as in the ipsilateral thalamus and basal ganglia. After comparing the two groups, only the cortical deactivation in ipsilateral SI in the early stimulation phase as well as the activation in contralateral SI and SII in the late stimulation block remained as statistically significant differences between the two groups. The psychophysical experiments yielded a significant age-dependent effect of CPT change with less difference in the older group which is in line with the significantly smaller alterations in maximal BOLD signal change in the contra- and ipsilateral SI found between the two groups. Healthy aging seems to be associated with a decrease in intracerebral inhibition as reflected by smaller negative BOLD signal changes during fMRI tasks. This finding could constitute an important link between age-related neurophysiological changes and behavioral alterations in humans.

Changes in Cerebral and Cerebellar Activation Patterns Induced by Short-term Sequence Learning of a Serial Reaction Time Task: an fMRI Study

Changes in Cerebral and Cerebellar Activation Patterns Induced by Short-term Sequence Learning of a Serial Reaction Time Task: an fMRI Study

FMRI Evidence of Acupoints Specificity in Two Adjacent Acupoints

Objectives. Acupoint specificity is the foundation of acupuncture treatment. The aim of this study is to investigate whether the acupoint specificity exists in two adjacent acupoints. Design and Setting. Two adjacent real acupoints, LR3 (Taichong) and ST44 (Neiting), and a nearby nonacupoint were selected. Thirty-three health volunteers were divided into three groups in random order, and each group only received acupuncture at one of the three points. While they received acupuncture, fMRI scan was performed. Results. The common cerebral activated areas responding to LR3 and ST44 included the contralateral primary somatosensory area (SI) and ipsilateral cerebellum. Acupuncture at LR3 specifically activated contralateral middle occipital gyrus, ipsilateral medial frontal gyrus, superior parietal lobe, middle temporal gyrus, rostral anterior cingulate cortex (rACC), lentiform nucleus, insula, and contralateral thalamus. Stimulation at ST44 selectively activated ipsilateral secondary somatosensory area (SII), contralateral middle frontal gyrus, inferior frontal gyrus, lingual gyrus, lentiform nucleus, and bilateral posterior cingulate cortex (PCC). Conclusions. Acupuncture at adjacent acupoints elicits distinct cerebral activation patterns, and those specific patterns might be involved in the mechanism of the specific therapeutic effects of different acupoints.

Non-verbal emotion communication training induces specific changes in brain function and structure

The perception of emotional cues from voice and face is essential for social interaction. However, this process is altered in various psychiatric conditions along with impaired social functioning. Emotion communication trainings have been demonstrated to improve social interaction in healthy individuals and to reduce emotional communication deficits in psychiatric patients. Here, we investigated the impact of a non-verbal emotion communication training (NECT) on cerebral activation and brain structure in a controlled and combined functional magnetic resonance imaging (fMRI) and voxel-based morphometry study. NECT-specific reductions in brain activity occurred in a distributed set of brain regions including face and voice processing regions as well as emotion processing- and motor-related regions presumably reflecting training-induced familiarization with the evaluation of face/voice stimuli. Training-induced changes in non-verbal emotion sensitivity at the behavioral level and the respective cerebral activation patterns were correlated in the face-selective cortical areas in the posterior superior temporal sulcus and fusiform gyrus for valence ratings and in the temporal pole, lateral prefrontal cortex and midbrain/thalamus for the response times. A NECT-induced increase in gray matter (GM) volume was observed in the fusiform face area. Thus, NECT induces both functional and structural plasticity in the face processing system as well as functional plasticity in the emotion perception and evaluation system. We propose that functional alterations are presumably related to changes in sensory tuning in the decoding of emotional expressions. Taken together, these findings highlight that the present experimental design may serve as a valuable tool to investigate the altered behavioral and neuronal processing of emotional cues in psychiatric disorders as well as the impact of therapeutic interventions on brain function and structure.

Activation of thalamus in motor imagery results from gating by hypnosis

The ability to mentally imagine the performance of automatic movements has been well-established being employed in sports and physiotherapy as a tool for motor learning and rehabilitation. This is probably mediated by engagement of the same brain areas as during real motor performance. Here we investigated the effect of hypnotic trance on the cerebral activation pattern engaged in motor imagery in 16 healthy, right-handed subjects using fMRI. Motor imagery as compared with rest was related to activations in the left medial frontal areas (preSMA/SMA), prefrontal- and frontal areas, putamen and inferior parietal areas. When compared with performance of the same movements motor imagery resulted in activation of the left middle frontal cortex, precuneus, and posterior cingulate. Under hypnotic trance there was one extra-activation in the left thalamus which occurred specifically in the motor imagery condition. The regional beta indices were highly correlated among the areas of the cortical-subcortical motor network. Our data accord with the notion that hypnotic trance enhances the motor control circuit engaged in motor imagery by modulating the gating function of the thalamus.

224 aEEG and NIRS During Transition after Birth

Background and aimsEasily applicable non-invasive devices to monitor cerebral activity and oxygenation continuously during neonatal transition and resuscitation are lacking. We aimed to identify a method of directly monitoring cerebral...

Quantitative Changes in Regional Cerebral Blood Flow Induced by Cold, Heat and Ischemic Pain

The development of arterial spin labeling methods has allowed measuring regional cerebral blood flow (rCBF) quantitatively and to show the pattern of cerebral activity associated with any state such as a sustained pain state or changes due to a neurotropic drug. The authors studied the differential effects of three pain conditions in 10 healthy subjects on a 3 Tesla scanner during resting baseline, heat, cold, and ischemic pain using continuous arterial spin labeling. Cold pain showed the greatest absolute rCBF increases in left anterior cingulate cortex, left amygdala, left angular gyrus, and Brodmann area 6, and a significant rCBF decrease in the cerebellum. Changes in rCBF were characteristic of the type of pain condition: cold and heat pain showed increases, whereas the ischemic condition showed a reduction in mean absolute gray matter flow compared with rest. An association of subjects' pain tolerance and cerebral blood flow was noted. The observation that quantitative rCBF changes are characteristic of the pain task used and that there is a consistent rCBF change in Brodman area 6, an area responsible for the integration of a motor response to pain, should provide extremely useful information in the quest to develop an imaging biomarker of pain. Conceivably, response in BA6 may serve as an objective measure of analgesic efficacy.

Resting State Abnormalities in Psychosis Compared to Acute Cannabinoids and Opioids Challenges: A Systematic Review of Functional Imaging Studies

We conducted a systematic review on resting state cerebral blood flow activities found in first-episode psychosis (FEP) and during acute effects of cannabinoids and opioids, mental states that can be profoundly different from normal functioning. The main goal was to identify connections of cerebral blood flow measure and regional brain activity patterns associated with subjective experiences and to find out whether there are similarities between the three mental states. The present study reviewed systematically the current state of research with respect to cannabinoids and opioids on resting state activity patterns as investigated by different neuroimaging techniques. Twenty-two studies encompassing different neuroimaging techniques were selected. Cerebral perfusion and resting blood flow measure by single-photon emission computed tomography (SPECT), positron emission tomography (PET), perfusion-weighted imaging (PWI), arterial spin labeling (ASL), and resting-state functional magnetic resonance imaging (resting-state fMRI) during acute cannabinoids or opioids challenges were compared to findings in patients with FEP. The total number of subjects included in this review encompassed 279 FEP/controls (mean age = 28 ± 8.6 years, 40.1% females), 315 participants with cannabinoids (mean age = 29 ± 7.1 years, 31.8% females) and 113 participants with opioids (mean age = 30 ± 3.9 years, 17.3% females). We found that effects on regional activity were highly conflicting within the same condition group. However, we critical compared baseline acitivty patterns between FEP and acute cannabinoid or opioids effects. There was some consistent evidence suggesting positive symptoms of FEP and depersonalization experiences after cannabis administration both result in an increased anterior cingulate activity, an important area in the default mode network.

An fMRI Investigation of the Cortical Network Underlying Detection and Categorization Abilities in Hemianopic Patients

The current study aims to investigate visual scene perception and its neuro-anatomical correlates for stimuli presented in the central visual field of patients with homonymous hemianopia, and thereby to assess the effect of a right or a left occipital lesion on brain reorganization. Fourteen healthy participants, three left brain damaged (LBD) patients with right homonymous hemianopia and five right brain damaged (RBD) patients with left homonymous hemianopia performed a visual detection task (i.e. "Is there an image on the screen?") and a categorization task (i.e. "Is it an image of a highway or a city?") during a block-designed functional magnetic resonance imaging recording session. Cerebral activity analyses of the posterior areas-the occipital lobe in particular-highlighted bi-hemispheric activation during the detection task but more lateralized, left occipital lobe activation during the categorization task in healthy participants. Conversely, in patients, the same network of activity was observed in both tasks. However, LBD patients showed a predominant activation in their right hemisphere (occipital lobe and posterior temporal areas) whereas RBD patients showed a more bilateral activation (in the occipital lobes). Overall, our preliminary findings suggest a specific pattern of cerebral activation depending on the task instruction in healthy participants and cerebral reorganization of the posterior areas following brain injury in hemianopic patients which could depend upon the side of the occipital lesion.

Cerebral Perfusion Differences Between Drowsy and Nondrowsy Individuals After Acute Sleep Restriction

To investigate changes in resting cerebral blood flow (CBF) after acute sleep restriction. To investigate the extent to which changes in CBF after sleep restriction are related to drowsiness as manifested in eye-video. Participants were scanned for 5 min using arterial spin labeling (ASL) perfusion imaging after both sleep-restricted and rested nights. Participants were rated for visual signs of drowsiness in the eye-video recorded during the scan. Lying supine in a 3-Tesla magnetic resonance imaging scanner. Twenty healthy adults (age 20-37 yr) with no history of neurologic, psychiatric, or sleep disorder, and with usual time in bed of 7.0-8.5 h. In the night before the sleep-restricted session, participants were restricted to 4 h time in bed. There was an overall reduction in CBF in the right-lateralized fronto-parietal attentional network after acute sleep restriction, although this was largely driven by participants who showed strong signs of drowsiness in the eye-video after sleep restriction. Change in CBF correlated with change in drowsiness in the basal forebrain-cingulate regions. In particular, there was a pronounced increase in CBF in the basal forebrain and anterior and posterior cingulate cortex of participants who remained alert after sleep restriction. The pattern of cerebral activity after acute sleep restriction is highly dependent on level of drowsiness. Nondrowsy individuals are able to increase activity in the arousal-promoting brain regions and maintain activity in attentional regions. In contrast, drowsy individuals are unable to maintain arousal and show decreased activity in both arousal-promoting and attentional regions.