Previous work using single-cell recordings in monkeys and neuro-imaging studies in humans has shown that perceiving an object or imaging the action associated with the object recruits the same brain regions in the ventral premotor cortex as performing an action with the object. We used functional magnetic resonance imaging (fMRI) for examining whether similar brain regions are also activated while maintaining information about manipulable objects in working memory. Holding information about manipulable objects in working memory activated the left ventral premotor cortex and the left inferior frontal gyrus (Broca's area). Conversely, non-manipulable objects to be held in working memory co-activated Broca's area and the left angular gyrus. When contrasted directly, manipulable relative to non-manipulable objects activated the left ventral premotor cortex and the anterior intraparietal sulcus, a circuitry that is assumed to mediate the transformation of movement-relevant object properties into hand actions. These results indicate that visual working memory for manipulable objects is based on motor programmes associated with their use. Similar to speech motor programmes in verbal memory tasks, hand motor programmes may allow the maintenance of objects in working memory over short intervals.

We examined the role of motor affordances of objects for working memory retention processes. Three experiments are reported in which participants passively viewed pictures of real world objects or had to retain the objects in working memory for a comparison with an S2 stimulus. Brain activation was recorded by means of functional magnetic resonance imaging (fMRI). Retaining information about objects for which hand actions could easily be retrieved (manipulable objects) in working memory activated the hand region of the ventral premotor cortex (PMC) contralateral to the dominant hand. Conversely, nonmanipulable objects activated the left inferior frontal gyrus. This suggests that working memory for objects with motor affordance is based on motor programs associated with their use. An additional study revealed that motor program activation can be modulated by task demands: Holding manipulable objects in working memory for an upcoming motor comparison task was associated with left ventral PMC activation. However, retaining the same objects for a subsequent size comparison task led to activation in posterior brain regions. This suggests that the activation of hand motor programs are under top down control. By this they can flexibly be adapted to various task demands. It is argued that hand motor programs may serve a similar working memory function as speech motor programs for verbalizable working memory contents, and that the premotor system mediates the temporal integration of motor representations with other task-relevant representations in support of goal oriented behavior.

Neuroimaging studies show that prefrontal, premotor, and parietal cortical regions are part of a working memory network that supports the active retention of information. In two experiments we used fMRI to examine whether prefrontal and posterior cortical areas are organized in a content‐specific way for object and spatial working memory. Subjects performed a delayed matching‐to‐sample task modified to allow the examination of content‐specific retention processes, independent of perceptual and decision‐related processes. In Experiment 1, either unfamiliar geometrical objects (Klingon letters from an artificial alphabet unknown to the participants) or their spatial locations had to be memorized, whereas in Experiment 2, either unfamiliar faces or biological objects (butterflies) were actively memorized. All tasks activated a similar cortical network including posterior parietal (banks of the intraparietal sulcus), premotor (banks of the inferior precentral sulcus) and prefrontal regions (banks of the inferior frontal sulcus), and the presupplementary motor area (pre‐SMA). For geometrical objects and faces for which strategic semantic processing can be assumed, this activation was larger in the left than in the right hemisphere, whereas a bilateral or right dominant distribution was obtained for butterflies and spatial locations. The present results do not support the process‐specific or content‐specific view of the role of the prefrontal cortex in working memory task. Rather, they suggest that the inferior prefrontal cortex houses nonmemonic strategic processing systems required for response selection and task management that can flexibly be used across a variety of tasks and informational domains. Hum. Brain Mapping 11:146–161, 2000. © 2000 Wiley‐Liss, Inc.

Neuroimaging studies show that prefrontal, premotor, and parietal cortical regions are part of a working memory network that supports the active retention of information. In two experiments we used fMRI to examine whether prefrontal and posterior cortical areas are organized in a content-specific way for object and spatial working memory. Subjects performed a delayed matching-to-sample task modified to allow the examination of content-specific retention processes, independent of perceptual and decision-related processes. In Experiment 1, either unfamiliar geometrical objects (Klingon letters from an artificial alphabet unknown to the participants) or their spatial locations had to be memorized, whereas in Experiment 2, either unfamiliar faces or biological objects (butterflies) were actively memorized. All tasks activated a similar cortical network including posterior parietal (banks of the intraparietal sulcus), premotor (banks of the inferior precentral sulcus) and prefrontal regions (banks of the inferior frontal sulcus), and the presupplementary motor area (pre-SMA). For geometrical objects and faces for which strategic semantic processing can be assumed, this activation was larger in the left than in the right hemisphere, whereas a bilateral or right dominant distribution was obtained for butterflies and spatial locations. The present results do not support the process-specific or content-specific view of the role of the prefrontal cortex in working memory task. Rather, they suggest that the inferior prefrontal cortex houses nonmemonic strategic processing systems required for response selection and task management that can flexibly be used across a variety of tasks and informational domains.

Behavioral variant frontotemporal dementia (bvFTD) is characterized by severe changes in personality/behavior. Recent studies have provided evidence that a decrease in serotonin receptors and neuronal loss in the raphe nuclei play a role in the bvFTD pathology. Serotonergic antidepressants have been reported to diminish behavioral disturbances in bvFTD, particularly repetitive behaviors, disinhibition, apathy, sexually inappropriate behaviors, and hyperorality. Here, we present the case of an 80-year-old Caucasian male patient with clinically and biomarker supported bvFTD (“probable” bvFTD; disease-specific alterations in ¹⁸F-fluorodesoxyglucose positron emission tomography and magnetic resonance imaging). The patient exhibited behavioral disinhibition, apathy, a loss of empathy, perseverative behavior during testing, hyperorality, changes in diet, and executive deficits in neuropsychological testing. Remarkably, he failed in solving crosswords by systematically filling in the blanks by letters in alphabetical order (A, B, C, D, etc.), indicating obsessive-compulsive behavior. One year later, the patient visited the clinic again for a follow-up investigation. He had taken 20 mg of citalopram per day for 1 consecutive year. Remarkably, he had regained the ability to fill in crossword puzzles correctly, although the neuropsychiatric inventory showed overall only small improvement in behavioral impairment. A regimen of 20 mg citalopram per day over the course of 1 year led to a specific improvement in one of the bvFTD core symptoms, obsessive-compulsive behavior, most pronounced in solving crossword puzzles. This case contributes to the understanding of the neuropharmacological correlates of bvFTD and supports the treatment of bvFTD’s behavioral symptoms with selective serotonin reuptake inhibitors.