Effects of visual information regarding tactile stimulation on the somatosensory cortical activation:a functional MRI study

Many studies have investigated the evidence for tactile and visual interactive responses to activation of various brain regions. However, few studies have reported on the effects of visuo-tactile multisensory inte-gration on the amount of brain activation on the somatosensory cortical regions. The aim of this study was to examine whether coincidental information obtained by tactile stimulation can affect the somatosensory cortical activation using functional MRI. Ten right-handed healthy subjects were recruited for this study. Two tasks (tactile stimulation and visuotactile stimulation) were performed using a block paradigm during fMRI scanning. In the tactile stimulation task, in subjects with eyes closed, tactile stimulation was applied on the dorsum of the right hand, corresponding to the proximal to distal directions, using a rubber brush. In the visuotactile stimulation task, tactile stimulation was applied to observe the attached mirror in the MRI chamber reflecting their hands being touched with the brush. In the result of SPM group analysis, we found brain activation on the somatosensory cortical area. Tactile stimulation task induced brain acti-vations in the left primary sensory-motor cortex (SM1) and secondary somatosensory cortex (S2). In the visuo-tactile stimulation task, brain activations were observed in the both SM1, both S2, and right posterior parietal cortex. In all tasks, the peak activation was detected in the contralateral SM1. We examined the ef-fects of visuo-tactile multisensory integration on the SM1 and found that visual information during tactile stimulation could enhance activations on SM1 compared to the tactile unisensory stimulation.     

Neural substrates for forward and backward recitation of numbers and the alphabet: a close examination of the role of intraparietal sulcus and perisylvian areas

Despite numerous studies on the neural basis of numerical processing, few studies have examined the neural substrates of one of the most basic numerical processing-number sequence recitation. The present study used fMRI to investigate neural substrates of number sequence recitation, focusing on the intraparietal sulcus (IPS) and perisylvian areas. This study used a 2 (number versus alphabet) x 2 (forward versus backward recitation) design. 12 Chinese undergraduates were asked to recite overtly but gently numerical and alphabetical sequences forward and backward. Results showed that, for both numerical and alphabetic sequences, the left IPS was activated when performing backward recitation, but not when performing forward recitation. In terms of perisylvian areas, all four tasks elicited activation in bilateral superior temporal gyrus and inferior frontal gyrus, but forward recitation elicited greater activation in the left posterior superior temporal gyrus than did backward recitation, whereas backward recitation elicited greater activation in the left inferior frontal gyrus than did forward recitation. These results suggest that forward recitation of numbers and the alphabet is typically based on verbal processing of numbers implemented in the perisylvian area, whereas backward recitation would likely require additional neural resources in the IPS.     

Changes in Regional Cerebral Oxidative Metabolism Induced by Tactile Learning and Recognition in Man

We measured the regional cerebral oxidative metabolism (rCMRO2) with positron emission tomography in normal healthy volunteers in three different stages: rest, tactile learning, and tactile recognition of complicated geometrical objects. The frequency of manipulatory movements during tactile recognition was twice that of tactile learning. Tactile recognition with the right hand increased rCMRO2 in six prefrontal cortical areas, bilaterally in the supplementary motor areas, the premotor areas and supplementary sensory areas, in the left primary motor and primary sensory area, in the left anterior superior parietal lobule, bilaterally in the secondary somatosensory area, the anterior insula, lingual gyri, hippocampus, basal ganglia, anterior parasagittal cerebellum, and lobus posterior cerebelli. These structures have in other studies been found to participate in manipulatory movements and analysis of somatosensory information. Tactile learning increased rCMRO2 in the same structures as did tactile recognition. Thus we found no differences in the anatomical structures participating in storage and retrieval. However the rCMRO2 increases in the left premotor cortex, supplementary motor area, and left somatosensory hand area were larger during tactile recognition in accordance with the higher frequency of manipulatory movements and higher flux of somatosensory information from the periphery during recognition. Despite this the rCMRO2 was significantly higher in the neocerebellar cortex during tactile learning. Since there were no learning effects on the manipulatory movements, this extra metabolic activity in the lateral cerebellum was attributed to energy demanding processes associated with climbing fibre activity during storage of somatosensory information.     

Viewing the body prepares the brain for touch: effects of TMS over somatosensory cortex

Viewing the body can improve tactile perception. We investigated whether this could be due to a remodeling of somatosensory cortical areas during vision of the body. Single-pulse transcranial magnetic stimulation (TMS) was delivered over the primary and secondary somatosensory areas of subjects who showed clear visual-tactile enhancement while they performed a tactile grating discrimination task. Before the tactile stimulus, subjects viewed either their right index finger through a semisilvered mirror or an object reflected by the mirror and positioned to appear in the same location as the finger. In a first experiment we observed that TMS over primary somatosensory cortex significantly reduced subjects' accuracy whilst viewing the hand. No such reduction was found when subjects viewed a neutral object. In a second experiment, we disrupted the activity of primary and secondary somatosensory areas in different sessions. When stimulating the primary somatosensory cortex, a reduction in accuracy was again found while viewing the hand, but not a neutral object. TMS over secondary somatosensory cortex had no effect in any condition. Our results show that vision of the body may act at an early stage in stimulus elaboration and perception, allowing an anticipatory tuning of the neural circuits in primary somatosensory cortex that underlie tactile acuity.     

Neural substrates of tactile object recognition: an fMRI study

A functional magnetic resonance imaging (fMRI) study was conducted during which seven subjects carried out naturalistic tactile object recognition (TOR) of real objects. Activation maps, conjunctions across subjects, were compared between tasks involving TOR of common real objects, palpation of "nonsense" objects, and rest. The tactile tasks involved similar motor and sensory stimulation, allowing higher tactile recognition processes to be isolated. Compared to nonsense object palpation, the most prominent activation evoked by TOR was in secondary somatosensory areas in the parietal operculum (SII) and insula, confirming a modality-specific path for TOR. Prominent activation was also present in medial and lateral secondary motor cortices, but not in primary motor areas, supporting the high level of sensory and motor integration characteristic of object recognition in the tactile modality. Activation in a lateral occipitotemporal area associated previously with visual object recognition may support cross-modal collateral activation. Finally, activation in medial temporal and prefrontal areas may reflect a common final pathway of modality-independent object recognition. This study suggests that TOR involves a complex network including parietal and insular somatosensory association cortices, as well as occipitotemporal visual areas, prefrontal, and medial temporal supramodal areas, and medial and lateral secondary motor cortices. It confirms the involvement of somatosensory association areas in the recognition component of TOR, and the existence of a ventrolateral somatosensory pathway for TOR in intact subjects. It challenges the results of previous studies that emphasize the role of visual cortex rather than somatosensory association cortices in higher-level somatosensory cognition.     

Cortical processing of tactile language in a postlingually deaf-blind subject

We compared neural activation detected by magnetoencephalography (MEG) during tactile presentation of words and non-words in a postlingually deaf-blind subject and six normal volunteers. The left postcentral gyrus, bilateral inferior frontal gyri, left posterior temporal lobe, right anterior temporal lobe, bilateral middle occipital gyri were activated when tactile words were presented to the right hand of the deaf-blind subject. This set of activated regions was not observed in the normal volunteers, although activation of several combinations of these regions was detected. Positron emission tomography confirmed the location of the MEG-activated areas in the deaf-blind subject. Our results demonstrated that the deaf-blind subject is heavily involved in interpreting tactile language by enhancing cortical activation of cognitive and semantic processing.     

Men versus women on sexual brain function: Prominent differences during tactile genital stimulation,but not during orgasm

Biological differences in male and female sexuality are obvious in the behavioral domain, but the central mechanisms that might explain these behavioral gender differences remain unclear. In this study, we merged two earlier positron emission tomography data sets to enable systematic comparison of the brain responses in heterosexual men and women during sexual tactile genital (penile and clitoral) stimulation and during orgasm. Gender commonalities were most evident during orgasm, a phase which demonstrated activations in the anterior lobe of the cerebellar vermis and deep cerebellar nuclei, and deactivations in the left ventromedial and orbitofrontal cortex in both men and women. During tactile genital stimulation, deactivations in the right amygdala and left fusiform gyrus were found for both genders. Marked gender differences were seen during this phase: left fronto‐parietal areas (motor cortices, somatosensory area 2 and posterior parietal cortex) were activated more in women, whereas in men, the right claustrum and ventral occipitotemporal cortex showed larger activation. The only prominent gender difference during orgasm was male‐biased activation of the periaqueductal gray matter. From these results, we conclude that during the sexual act, differential brain responses across genders are principally related to the stimulatory (plateau) phase and not to the orgasmic phase itself. These results add to a better understanding of the neural underpinnings of human sexuality, which might benefit treatment of psychosexual disorders. Hum Brain Mapp 2009. © 2009 Wiley‐Liss, Inc.     

Brain processing of capsaicin-induced secondary hyperalgesia: a functional MRI study.

OBJECTIVE: To investigate, using functional MRI (fMRI), the neural network that is activated by the pain component of capsaicin-induced secondary mechanical hyperalgesia. BACKGROUND: Mechanical hyperalgesia (i.e., pain to innocuous tactile stimuli) is a distressing symptom of neuropathic pain syndromes. Animal experiments suggest that alterations in central pain processing occur that render tactile stimuli capable of activating central pain-signaling neurons. A similar central sensitization can be produced experimentally with capsaicin. METHODS: In nine healthy individuals the cerebral activation pattern resulting from cutaneous nonpainful mechanical stimulation at the dominant forearm was imaged using fMRI. Capsaicin was injected adjacent to the stimulation site to induce secondary mechanical hyperalgesia. The identical mechanical stimulation was then perceived as painful without changing the stimulus intensity and location. Both activation patterns were compared to isolate the specific pain-related component of mechanical hyperalgesia from the tactile component. RESULTS: The pattern during nonpainful mechanical stimulation included contralateral primary sensory cortex (SI) and bilateral secondary sensory cortex (SII) activity. During hyperalgesia, significantly higher activation was found in the contralateral prefrontal cortex: the middle (Brodmann areas [BAs] 6, 8, and 9) and inferior frontal gyrus (BAs 44 and 45). No change was present within SI, SII, and the anterior cingulate cortex. CONCLUSIONS: Prefrontal activation is interpreted as a consequence of attention, cognitive evaluation, and planning of motor behavior in response to pain. The lack of activation of the anterior cingulate contrasts with physiologic pain after C-nociceptor stimulation. It might indicate differences in the processing of hyperalgesia and C-nociceptor pain or it might be due to habituation of affective sensations during hyperalgesia compared with acute capsaicin pain.     

Activation of SI is modulated by attention: a random effects fMRI study using mechanical stimuli

Animal experiments on tactile attention suggest a modulation of sensory processing on the level of sensory representations but correspondent neuroimaging data in humans is inconclusive. The present experiment used mechanical stimuli to study tactile processing while varying the focus of attention. Activations were contrasted between attend and ignore conditions, both of which employed identical stimulation characteristics and an active task. Random effects analysis revealed significant attention effects in area SI (primary somatosensory cortex) in that the blood oxygenation level-dependent response was greater for attended than for ignored stimuli. Modulations were further found in the secondary somatosensory cortex and the middle temporal gyrus. These findings suggest that stimulus processing at the level of primary representations in area SI is modulated by attention.     

Neuronal responses to the scratching and caressing of one's own skin in patients with skin‐picking disorder

Skin‐picking disorder (SPD) is a common mental disorder. The predominant symptom involves the repeated scratching and picking of one's own skin. This behavior causes severe tissue damage (sores, scars, and infections), often leading to disfigurement. Besides physical injury, SPD is associated with clinically significant distress and impairment in important areas of functioning. The neurobiological mechanisms of SPD are still poorly understood. In this study, 30 SPD patients and 31 control participants (35 women, 26 men) with a mean age of 34 years were instructed to either scratch or gently stroke a small skin area on their arms during functional magnetic resonance imaging. Gender‐specific effects were revealed. In the female sample, SPD patients showed less activation in the middle frontal gyrus (MFG) and primary/secondary somatosensory cortices during caressing relative to scratching than controls. In addition, contrasting caressing with a rest condition revealed reduced activation in the somatosensory cortex (concerned with the decoding and integration of tactile information) and the MFG (attention/cognitive monitoring) in female patients. No differential brain activation was found in the male sample. This symptom provocation study hints at a reduced sensitivity of pleasant touch in women with SPD.     

Direct current stimulation over the human sensorimotor cortex modulates the brain's hemodynamic response to tactile stimulation

Tactile stimuli produce afferent signals that activate specific regions of the cerebral cortex. Noninvasive transcranial direct current stimulation (tDCS) effectively modulates cortical excitability. We therefore hypothesised that a single session of tDCS targeting the sensory cortices would alter the cortical response to tactile stimuli. This hypothesis was tested with a block‐design functional magnetic resonance imaging protocol designed to quantify the blood oxygen level‐dependent response to controlled sinusoidal pressure stimulation applied to the right foot sole, as compared with rest, in 16 healthy young adults. Following sham tDCS, right foot sole stimulation was associated with activation bilaterally within the precentral cortex, postcentral cortex, middle and superior frontal gyri, temporal lobe (subgyral) and cingulate gyrus. Activation was also observed in the left insula, middle temporal lobe, superior parietal lobule, supramarginal gyrus and thalamus, as well as the right inferior parietal lobule and claustrum (false discovery rate corrected, P < 0.05). To explore the regional effects of tDCS, brain regions related to somatosensory processing, and cortical areas underneath each tDCS electrode, were chosen as regions of interest. Real tDCS, as compared with sham tDCS, increased the percent signal change associated with foot stimulation relative to rest in the left posterior paracentral lobule. These results indicate that tDCS acutely modulated the cortical responsiveness to controlled foot pressure stimuli in healthy adults. Further study is warranted, in both healthy individuals and patients with sensory impairments, to link tDCS‐induced modulation of the cortical response to tactile stimuli with changes in somatosensory perception.     

Distinct and shared cerebral activations in processing innocuous versus noxious contact heat revealed by functional magnetic resonance imaging

Whether innocuous heat (IH)‐exclusive brain regions exist and whether patterns of cerebral responses to IH and noxious heat (NH) stimulations are similar remain elusive. We hypothesized that distinct and shared cerebral networks were evoked by each type of stimulus. Twelve normal subjects participated in a functional MRI study with rapidly ramped IH (38°C) and NH (44°C) applied to the foot. Group activation maps demonstrated three patterns of cerebral activation: (1) IH‐responsive only in the inferior parietal lobule (IPL); (2) NH‐responsive only in the primary somatosensory cortex (S1), secondary somatosensory cortex (S2), posterior insular cortex (IC), and premotor area (PMA); and (3) both IH‐ and NH‐responsive in the middle frontal gyrus, inferior frontal gyrus (IFG), anterior IC, cerebellum, superior frontal gyrus, supplementary motor area, thalamus, anterior cingulate cortex (ACC), lentiform nucleus (LN), and midbrain. According to the temporal analysis of regions of interest, the IPL exclusively responded to IH, and the S2, posterior IC, and PMA were exclusively activated by NH throughout the entire period of stimulation. The IFG, thalamus, ACC, and LN responded differently during different phases of IH versus NH stimulation, and the NH‐responsive‐only S1 responded transiently during the early phase of IH stimulation. BOLD signals in bilateral IPLs were specifically correlated with the ratings of IH sensation, while responses in the contralateral S1 and S2 were correlated with pain intensity. These results suggest that distinct and shared spatial and temporal patterns of cerebral networks are responsible for the perception of IH and NH. Hum Brain Mapp, 2010. © 2009 Wiley‐Liss, Inc.     

Effects of stimulus presentation rate on the activity of primary somatosensory cortex: a functional magnetic resonance imaging study in humans

To investigate the effect of stimulus presentation rate on the activity of primary somatosensory cortex, we performed echo-planar functional magnetic resonance imaging using a 1.5-tesla magnetic resonance system. Eight right-handed normal volunteers underwent functional magnetic resonance imaging during somatosensory stimulation with a 0.2 ms electrical square wave to the left index finger at 1, 4, 8, 16, and 32 Hz at constant intensity. Activated areas were located mainly around 'the hand area' of the right postcentral gyrus. Between 4 and 16 Hz, almost all subjects showed significant activation, but at 1 Hz and 32 Hz, five of eight subjects showed no activation. The average number of activated pixels in this area between 4 and 16 Hz were significantly greater than those at 1 Hz and 32 Hz, and the average percent signal increase had its activation peak at 8 Hz. Our results suggest that the existence of the optimal stimulation rate range may be a common phenomenon to a variety of sensory modalities. The electrical somatosensory stimulation rates from 4 Hz to 16 Hz are advisable to investigate the activation of the primary somatosensory cortex in human subjects.     

Human brain mapping of auditory imagery: event-related functional MRI study

We used event-related fMRI methodology to investigate human brain activity during auditory imagery. A series of susceptibility-weighted MR images covering the whole brain were acquired to obtain blood oxygenation level-dependent (BOLD) signal changes associated with the imagery event of hearing simple monotone. Group analysis across the 12 right-handed subjects revealed activations in the medial and inferior frontal gyri, precuneus, middle frontal gyri, superior temporal gyri, and anterior cingulate gyri. Bilateral primary and secondary auditory areas in the superior temporal gyri also exhibited the event-related MR signal changes. The proposed method allowed for the analysis of brain areas responsive to the event of auditory imagery while our results suggest that auditory imagery and actual audition share common neural substrates.     

Somatosensory cortical activations are suppressed in patients with tactile extinction: a PET study

OBJECTIVE: To investigate whether tactile extinction alters the cortical somatosensory activations induced by hand vibration. BACKGROUND: Tactile extinction occurs mainly after right-brain lesions and consists of the inability to perceive a contralesional cutaneous stimulation when a similar stimulus is applied to the mirror region of the ipsilesional hemibody. The pathophysiology of tactile extinction is poorly understood, but it is considered to be a deficit of selective attention of somatosensory stimuli. Although other theories have been proposed, our understanding of the pathophysiology of tactile extinction may benefit from functional imaging studies. METHODS: We selected three patients with pure tactile extinction and a mainly subcortical right-brain lesion that spared the primary sensorimotor cortex (SM1). We used PET to investigate the responses to unilateral and bilateral hand vibration in SM1 and the secondary somatosensory cortical area (SII). RESULTS: During bilateral hand vibration, activation was normal in the left SM1, suppressed in the right SM1, and markedly decreased in both SII, which was consistent with the extinction of the left-hand stimulus. During unilateral left-hand vibration, the activation of the right SM1 was still markedly impaired, but the activation of both SII was normal. CONCLUSIONS: We found marked changes in the activation of cortical somatosensory areas induced by hand vibration in patients with tactile extinction. The role of selective attention in cortical activation is also examined.     

Passive tactile recognition of geometrical shape in humans: An fMRI study

Tactile shape discrimination involves frontal other than somatosensory cortex (Palva et al., 2005 [48]), but it is unclear if this frontal activity is related to exploratory concomitants. In this study, we investigated topographical details of prefrontal, premotor, and parietal areas during passive tactile recognition of 2D geometrical shapes in conditions avoiding exploratory movements. Functional magnetic resonance imaging (fMRI) was performed while the same wooden 2D geometrical shapes were blindly pressed on subjects’ passive right palm in three conditions. In the RAW condition, shapes were pressed while subjects were asked to attend to the stimuli but were not trained to recognize them. After a brief training, in the SHAPE condition subjects were asked to covertly recognize shapes. In the RECOGNITION condition, they were asked to overtly recognize shapes, using response buttons with their opposite hand. Results showed that somatosensory cortex including contralateral SII, contralateral SI, and left insula was active in all conditions, confirming its importance in processing tactile shapes. In the RAW vs. SHAPE contrast, bilateral posterior parietal, insular, premotor, prefrontal, and (left) Broca's areas were more active in the latter. In the RECOGNITION, activation of (left) Broca's area correlated with correct responses. These results suggest that, even without exploratory movements, passive recognition of tactile geometrical shapes involves prefrontal and premotor as well as somatosensory regions. In this framework, Broca's area might be involved in a successful selection and/or execution of the correct responses.     

Recovery from hemineglect: Differential neurobiological effects of optokinetic stimulation and alertness training

We prospectively investigated by means of neuropsychological tests and functional magnetic resonance imaging (fMRI) the behavioural and neural effects of a 3-week optokinetic stimulation (OKS) training in 7 patients with chronic visuospatial neglect resulting from right-hemisphere lesions. Behaviourally, OKS caused both a short- and a long-term (4 weeks) improvement of performance in a neglect test battery (compared to a 3-week baseline period). This amelioration of neglect symptoms was associated with increases of neural activity during an fMRI spatial attention task bilaterally in the middle frontal gyrus and the precuneus. Additional left hemisphere increases in neural activity were observed in the cingulate gyrus, angular gyrus, middle temporal gyrus and occipital cortex. This pattern of activation represents a combination of areas normally involved in spatial attention plus a compensatory recruitment of left hemisphere areas. These results were then compared with data from our previous study (Thimm et al., 2006) which employed an alertness training (AIXTENT) with an otherwise identical treatment study design. After the OKS training there was more activation bilaterally in the precuneus than after the AIXTENT training. In contrast, after AIXTENT training there was more activation bilaterally in frontal cortex. Taken together, the results show that amelioration of neglect can be induced by both OKS and alertness training. The data furthermore suggest that the differential activations of frontal or parietal areas may reflect the specific impact of the two types of training either on an anterior system for the control of attention intensity (AIXTENT) or on the posterior system of spatial attention (OKS).     

Pain-related somatosensory evoked magnetic fields induced by controlled ballistic mechanical impacts.

The purpose of this study was to investigate cortical processing of painful compared with tactile mechanical stimulation by means of magnetoencephalography (MEG) using the novel technique of mechanical impact loading. A light, hard projectile is accelerated pneumatically in a guiding barrel and elicits a brief sensation of pain when hitting the skin in free flight. Controllable noxious and innocuous impact velocities facilitate the generation of different, predetermined stimulus intensities. The authors applied painful as well as tactile mechanical impacts to the dorsum of the second, third, and fourth digit of the nondominant hand. Pain-related somatosensory evoked magnetic fields (SSEFs) were compared with those following tactile stimulation in seven healthy volunteers. Contralateral primary sensory cortical area activation was observed within the first 70 msec after tactile as well as painful stimulus intensities. Only painful impacts elicited SSEF responses assigned to the bilateral secondary sensory cortical regions and to the middle part of the contralateral cingulate gyrus, which were active at latency ranges of 55 to 155 msec and 90 to 220 msec respectively. Additional long-latency responses occurred in these cortical areas as long as 280 msec after painful stimulation in three subjects. In contrast to tactile stimulation, painful mechanical impacts elicited SSEF responses in cortical areas demonstrated to be involved in central pain processing by previous MEG and neuroimaging studies. Because of its similarity to natural noxious stimuli and the possibility of adjustable painful and tactile impact velocities, the technique of mechanical impact loading provides a useful method for the neurophysiologic evaluation of cortical pain perception.     

Comparison Between a Real Sequential Finger and Imagery Movements: An fMRI Study Revisited

Recently, much discussion has been centered on the brain networks of recall, memory, and execution. This study utilized functional magnetic resonance imaging to compare activation between a simple sequential finger movement (real task) and recalling the same task (imagery task) in 15 right-handed normal subjects. The results demonstrated a greater activation in the contralateral motor and somatosensory cortex during the real task, and a higher activation in the contralateral inferior frontal cortex, ipsilateral motor, somatosensory cortex, and midbrain during the imagery task. These real task-specific areas and imagery-specific areas, including the ipsilateral motor and somatosensory cortex, are consistent with recent studies. However, this is the first report to demonstrate that the imagery-specific regions involve the ipsilateral inferior frontal cortex and midbrain. Directly comparing the activation between real and imagery tasks demonstrated the inferior frontal cortex and midbrain to therefore play important roles in cognitive feedback.     

The neural substrates associated with attentional resources and difficulty of concurrent processing of the two verbal tasks

The kana pick-out test has been widely used in Japan to evaluate the ability to divide attention in both adult and pediatric patients. However, the neural substrates underlying the ability to divide attention using the kana pick-out test, which requires participants to pick out individual letters (vowels) in a story while also reading for comprehension, thus requiring simultaneous allocation of attention to both activities, are still unclear. Moreover, outside of the clinical area, neuroimaging studies focused on the mechanisms of divided attention during complex story comprehension are rare. Thus, the purpose of the present study, to clarify the neural substrates of kana pick-out test, improves our current understanding of the basic neural mechanisms of dual task performance in verbal memory function. We compared patterns of activation in the brain obtained during performance of the individual tasks of vowel identification and story comprehension, to levels of activation when participants performed the two tasks simultaneously during the kana pick-out test. We found that activations of the left dorsal inferior frontal gyrus and superior parietal lobule increase in functional connectivity to a greater extent during the dual task condition compared to the two single task conditions. In contrast, activations of the left fusiform gyrus and middle temporal gyrus, which are significantly involved in picking out letters and complex sentences during story comprehension, respectively, were reduced in the dual task condition compared to during the two single task conditions. These results suggest that increased activations of the dorsal inferior frontal gyrus and superior parietal lobule during dual task performance may be associated with the capacity for attentional resources, and reduced activations of the left fusiform gyrus and middle temporal gyrus may reflect the difficulty of concurrent processing of the two tasks. In addition, the increase in synchronization between the left dorsal inferior frontal gyrus and superior parietal lobule in the dual task condition may induce effective communication between these brain regions and contribute to more attentional processing than in the single task condition, due to greater and more complex demands on voluntary attentional resources.