PMC:2570072 / 1041-6391 JSONTXT

{"project":"2_test","denotations":[{"id":"18982114-2918358-38625766","span":{"begin":202,"end":206},"obj":"2918358"},{"id":"18982114-4998337-38625767","span":{"begin":230,"end":234},"obj":"4998337"},{"id":"18982114-7233192-38625768","span":{"begin":255,"end":259},"obj":"7233192"},{"id":"18982114-7695894-38625769","span":{"begin":276,"end":280},"obj":"7695894"},{"id":"18982114-3185711-38625770","span":{"begin":293,"end":297},"obj":"3185711"},{"id":"18982114-7233192-38625771","span":{"begin":1395,"end":1399},"obj":"7233192"},{"id":"18982114-3185711-38625772","span":{"begin":1412,"end":1416},"obj":"3185711"},{"id":"18982114-3185711-38625773","span":{"begin":1911,"end":1915},"obj":"3185711"},{"id":"18982114-3185711-38625774","span":{"begin":2624,"end":2628},"obj":"3185711"},{"id":"18982114-2918358-38625775","span":{"begin":2992,"end":2996},"obj":"2918358"},{"id":"18982114-2918358-38625776","span":{"begin":3139,"end":3143},"obj":"2918358"},{"id":"18982114-10365959-38625777","span":{"begin":3612,"end":3616},"obj":"10365959"},{"id":"18982114-2918358-38625778","span":{"begin":3833,"end":3837},"obj":"2918358"},{"id":"18982114-2341879-38625779","span":{"begin":3839,"end":3843},"obj":"2341879"},{"id":"18982114-1875255-38625780","span":{"begin":3845,"end":3849},"obj":"1875255"},{"id":"18982114-10365959-38625781","span":{"begin":5029,"end":5033},"obj":"10365959"}],"text":"Introduction\nSince the beginning of the seventies, experiments on awake monkeys performing memory tasks have provided a wealth of information about the neural basis of working memory (Funahashi et al., 1989; Fuster and Alexander, 1971; Fuster and Jervey, 1981; Goldman-Rakic, 1995; Miyashita, 1988). During these experiments, the animals are trained to perform a task in which they have to remember for short times the identity or the location of a visual stimulus. These tasks share in common a ‘delay period’ during which the monkey has to maintain in ‘working’ memory information needed to solve the task after the end of the delay period. One of the major findings of these experiments is that neurons in several areas of the association cortex (e.g. prefrontal cortex, posterior parietal cortex and inferotemporal cortex) exhibit selective ‘persistent activity’ during delay period – they increase their firing rates compared to the baseline period, selectively for one or several cues whose identity is needed for the monkey to perform the task correctly after the end of the delay period.\nThree examples of such experiments are shown in Figure 1. The first example (Figure 1A) shows an example of an ‘object’ working memory task (memory of the identity of a stimulus). This type of short-term memory has been investigated by the delay-match-to-sample (DMS) experiment (Fuster and Jervey, 1981; Miyashita, 1988) in which the animal is required to retain the identity of a sample stimulus (an image shown on a computer screen) during the delay interval, and respond differently if the following test stimulus was identical or different from the sample stimulus. Figure 1A shows rasters and trial-averaged firing rates of a cell recorded in IT cortex, both in the case in which the presented stimulus was familiar (left panel), and in the case in which the stimulus was unfamiliar (right panel) (Miyashita, 1988). For stimuli that are familiar, the elevated rate distribution during the delay period is stimulus specific, i.e. each visual stimulus evokes a characteristic pattern of delay activity. When unfamiliar stimuli are presented, the recorded neurons may have elevated selective rates during stimulation, but no delay activity after the stimulus is removed.\nFigure 1 Experimental evidence of persistent activity. (A) Persistent activity of a cell in IT cortex of a monkey performing a DMS task. Raster and trial-averaged firing rate of in trials during which the picture that elicits the highest delay activity is shown as a sample (left) and trials when an unfamiliar picture is shown (right). From Miyashita (1988), reprinted by permission from Nature, © 1988 Macmillan Publishers Ltd. (B) Persistent activity of a cell in PFC of a monkey performing an ODR task. Raster and trial-averaged firing rate of a neuron when a cue is presented at 270 (top panel), the preferred cue location for that neuron (C: cue period; D: delay period; R: response period). From Funahashi et al. (1989), used with permission. (C) average firing rate during the delay period vs. cue location, for the neuron shown in (B). From Funahashi et al. (1989), used with permission. (D) Persistent activity of a cell in PFC of a monkey performing a delayed somatosensory discrimination task. Top panel: Rastergrams of a PFC cell arranged according to frequency of the base stimulus (indicated on the left). Middle panel: Trial averaged firing rate for several stimulus frequencies showing the monotonic response as a function of stimulus frequency. Bottom panel: Tuning curve of the cell in the delay period. From Romo et al. (1999), reprinted by permission from Nature, © 1989 Macmillan Publishers Ltd. The second example, shown in Figure 1B, presents a ‘spatial’ working memory task, the oculomotor-delayed-response (ODR) task (Funahashi et al., 1989, 1990, 1991) in which the animal is required to remember the location of a light spot on a screen during the delay interval, and respond at the end of the delay interval, making a saccade towards this location. Figure 1B shows rasters and trial averaged firing rate of a cell recorded in the PF cortex during the four phases of the task: in the first phase the monkey fixates a central spot on a screen; in the second phase a light spot at one of eight possible angles is presented (in this period the monkey continues to fixate the central spot); the third phase is the ‘delay period’ which starts with the removal of the stimulus and lasts for some seconds; finally, when the central spot disappears the monkey has to respond by making a saccade towards the location of the presented stimulus. Figure 1C shows the activity of the recorded cell during the delay period: this activity is maximal at a particular cue location (270°) and decreases away from that preferred location. This stimulus-selective, spatially tuned delay activity is observed for many of the recorded cells in PFC.\nOur last example is shown in Figure 1D. It represents a ‘parametric’ working memory task (Romo et al., 1999). In this task a monkey was trained to compare and discriminate the frequencies of two vibrotactile stimuli separated by a delay period. Figure 1D shows a cell in the inferior convexity that has persistent activity that varies monotonically with the cue frequency (indicated on the left and by the different curves)."}

{"project":"TEST0","denotations":[{"id":"18982114-189-197-765915","span":{"begin":202,"end":206},"obj":"[\"2918358\"]"},{"id":"18982114-217-225-765916","span":{"begin":230,"end":234},"obj":"[\"4998337\"]"},{"id":"18982114-232-240-765917","span":{"begin":255,"end":259},"obj":"[\"7233192\"]"},{"id":"18982114-225-233-765918","span":{"begin":276,"end":280},"obj":"[\"7695894\"]"},{"id":"18982114-230-238-765919","span":{"begin":293,"end":297},"obj":"[\"3185711\"]"},{"id":"18982114-119-127-765920","span":{"begin":1395,"end":1399},"obj":"[\"7233192\"]"},{"id":"18982114-136-144-765921","span":{"begin":1412,"end":1416},"obj":"[\"3185711\"]"},{"id":"18982114-234-242-765922","span":{"begin":1911,"end":1915},"obj":"[\"3185711\"]"},{"id":"18982114-16-24-765923","span":{"begin":2624,"end":2628},"obj":"[\"3185711\"]"},{"id":"18982114-23-31-765924","span":{"begin":2992,"end":2996},"obj":"[\"2918358\"]"},{"id":"18982114-23-31-765925","span":{"begin":3139,"end":3143},"obj":"[\"2918358\"]"},{"id":"18982114-18-26-765926","span":{"begin":3612,"end":3616},"obj":"[\"10365959\"]"},{"id":"18982114-144-152-765927","span":{"begin":3833,"end":3837},"obj":"[\"2918358\"]"},{"id":"18982114-150-158-765928","span":{"begin":3839,"end":3843},"obj":"[\"2341879\"]"},{"id":"18982114-156-164-765929","span":{"begin":3845,"end":3849},"obj":"[\"1875255\"]"},{"id":"18982114-63-71-765930","span":{"begin":5029,"end":5033},"obj":"[\"10365959\"]"}],"text":"Introduction\nSince the beginning of the seventies, experiments on awake monkeys performing memory tasks have provided a wealth of information about the neural basis of working memory (Funahashi et al., 1989; Fuster and Alexander, 1971; Fuster and Jervey, 1981; Goldman-Rakic, 1995; Miyashita, 1988). During these experiments, the animals are trained to perform a task in which they have to remember for short times the identity or the location of a visual stimulus. These tasks share in common a ‘delay period’ during which the monkey has to maintain in ‘working’ memory information needed to solve the task after the end of the delay period. One of the major findings of these experiments is that neurons in several areas of the association cortex (e.g. prefrontal cortex, posterior parietal cortex and inferotemporal cortex) exhibit selective ‘persistent activity’ during delay period – they increase their firing rates compared to the baseline period, selectively for one or several cues whose identity is needed for the monkey to perform the task correctly after the end of the delay period.\nThree examples of such experiments are shown in Figure 1. The first example (Figure 1A) shows an example of an ‘object’ working memory task (memory of the identity of a stimulus). This type of short-term memory has been investigated by the delay-match-to-sample (DMS) experiment (Fuster and Jervey, 1981; Miyashita, 1988) in which the animal is required to retain the identity of a sample stimulus (an image shown on a computer screen) during the delay interval, and respond differently if the following test stimulus was identical or different from the sample stimulus. Figure 1A shows rasters and trial-averaged firing rates of a cell recorded in IT cortex, both in the case in which the presented stimulus was familiar (left panel), and in the case in which the stimulus was unfamiliar (right panel) (Miyashita, 1988). For stimuli that are familiar, the elevated rate distribution during the delay period is stimulus specific, i.e. each visual stimulus evokes a characteristic pattern of delay activity. When unfamiliar stimuli are presented, the recorded neurons may have elevated selective rates during stimulation, but no delay activity after the stimulus is removed.\nFigure 1 Experimental evidence of persistent activity. (A) Persistent activity of a cell in IT cortex of a monkey performing a DMS task. Raster and trial-averaged firing rate of in trials during which the picture that elicits the highest delay activity is shown as a sample (left) and trials when an unfamiliar picture is shown (right). From Miyashita (1988), reprinted by permission from Nature, © 1988 Macmillan Publishers Ltd. (B) Persistent activity of a cell in PFC of a monkey performing an ODR task. Raster and trial-averaged firing rate of a neuron when a cue is presented at 270 (top panel), the preferred cue location for that neuron (C: cue period; D: delay period; R: response period). From Funahashi et al. (1989), used with permission. (C) average firing rate during the delay period vs. cue location, for the neuron shown in (B). From Funahashi et al. (1989), used with permission. (D) Persistent activity of a cell in PFC of a monkey performing a delayed somatosensory discrimination task. Top panel: Rastergrams of a PFC cell arranged according to frequency of the base stimulus (indicated on the left). Middle panel: Trial averaged firing rate for several stimulus frequencies showing the monotonic response as a function of stimulus frequency. Bottom panel: Tuning curve of the cell in the delay period. From Romo et al. (1999), reprinted by permission from Nature, © 1989 Macmillan Publishers Ltd. The second example, shown in Figure 1B, presents a ‘spatial’ working memory task, the oculomotor-delayed-response (ODR) task (Funahashi et al., 1989, 1990, 1991) in which the animal is required to remember the location of a light spot on a screen during the delay interval, and respond at the end of the delay interval, making a saccade towards this location. Figure 1B shows rasters and trial averaged firing rate of a cell recorded in the PF cortex during the four phases of the task: in the first phase the monkey fixates a central spot on a screen; in the second phase a light spot at one of eight possible angles is presented (in this period the monkey continues to fixate the central spot); the third phase is the ‘delay period’ which starts with the removal of the stimulus and lasts for some seconds; finally, when the central spot disappears the monkey has to respond by making a saccade towards the location of the presented stimulus. Figure 1C shows the activity of the recorded cell during the delay period: this activity is maximal at a particular cue location (270°) and decreases away from that preferred location. This stimulus-selective, spatially tuned delay activity is observed for many of the recorded cells in PFC.\nOur last example is shown in Figure 1D. It represents a ‘parametric’ working memory task (Romo et al., 1999). In this task a monkey was trained to compare and discriminate the frequencies of two vibrotactile stimuli separated by a delay period. Figure 1D shows a cell in the inferior convexity that has persistent activity that varies monotonically with the cue frequency (indicated on the left and by the different curves)."}

{"project":"0_colil","denotations":[{"id":"18982114-2918358-765915","span":{"begin":202,"end":206},"obj":"2918358"},{"id":"18982114-4998337-765916","span":{"begin":230,"end":234},"obj":"4998337"},{"id":"18982114-7233192-765917","span":{"begin":255,"end":259},"obj":"7233192"},{"id":"18982114-7695894-765918","span":{"begin":276,"end":280},"obj":"7695894"},{"id":"18982114-3185711-765919","span":{"begin":293,"end":297},"obj":"3185711"},{"id":"18982114-7233192-765920","span":{"begin":1395,"end":1399},"obj":"7233192"},{"id":"18982114-3185711-765921","span":{"begin":1412,"end":1416},"obj":"3185711"},{"id":"18982114-3185711-765922","span":{"begin":1911,"end":1915},"obj":"3185711"},{"id":"18982114-3185711-765923","span":{"begin":2624,"end":2628},"obj":"3185711"},{"id":"18982114-2918358-765924","span":{"begin":2992,"end":2996},"obj":"2918358"},{"id":"18982114-2918358-765925","span":{"begin":3139,"end":3143},"obj":"2918358"},{"id":"18982114-10365959-765926","span":{"begin":3612,"end":3616},"obj":"10365959"},{"id":"18982114-2918358-765927","span":{"begin":3833,"end":3837},"obj":"2918358"},{"id":"18982114-2341879-765928","span":{"begin":3839,"end":3843},"obj":"2341879"},{"id":"18982114-1875255-765929","span":{"begin":3845,"end":3849},"obj":"1875255"},{"id":"18982114-10365959-765930","span":{"begin":5029,"end":5033},"obj":"10365959"}],"text":"Introduction\nSince the beginning of the seventies, experiments on awake monkeys performing memory tasks have provided a wealth of information about the neural basis of working memory (Funahashi et al., 1989; Fuster and Alexander, 1971; Fuster and Jervey, 1981; Goldman-Rakic, 1995; Miyashita, 1988). During these experiments, the animals are trained to perform a task in which they have to remember for short times the identity or the location of a visual stimulus. These tasks share in common a ‘delay period’ during which the monkey has to maintain in ‘working’ memory information needed to solve the task after the end of the delay period. One of the major findings of these experiments is that neurons in several areas of the association cortex (e.g. prefrontal cortex, posterior parietal cortex and inferotemporal cortex) exhibit selective ‘persistent activity’ during delay period – they increase their firing rates compared to the baseline period, selectively for one or several cues whose identity is needed for the monkey to perform the task correctly after the end of the delay period.\nThree examples of such experiments are shown in Figure 1. The first example (Figure 1A) shows an example of an ‘object’ working memory task (memory of the identity of a stimulus). This type of short-term memory has been investigated by the delay-match-to-sample (DMS) experiment (Fuster and Jervey, 1981; Miyashita, 1988) in which the animal is required to retain the identity of a sample stimulus (an image shown on a computer screen) during the delay interval, and respond differently if the following test stimulus was identical or different from the sample stimulus. Figure 1A shows rasters and trial-averaged firing rates of a cell recorded in IT cortex, both in the case in which the presented stimulus was familiar (left panel), and in the case in which the stimulus was unfamiliar (right panel) (Miyashita, 1988). For stimuli that are familiar, the elevated rate distribution during the delay period is stimulus specific, i.e. each visual stimulus evokes a characteristic pattern of delay activity. When unfamiliar stimuli are presented, the recorded neurons may have elevated selective rates during stimulation, but no delay activity after the stimulus is removed.\nFigure 1 Experimental evidence of persistent activity. (A) Persistent activity of a cell in IT cortex of a monkey performing a DMS task. Raster and trial-averaged firing rate of in trials during which the picture that elicits the highest delay activity is shown as a sample (left) and trials when an unfamiliar picture is shown (right). From Miyashita (1988), reprinted by permission from Nature, © 1988 Macmillan Publishers Ltd. (B) Persistent activity of a cell in PFC of a monkey performing an ODR task. Raster and trial-averaged firing rate of a neuron when a cue is presented at 270 (top panel), the preferred cue location for that neuron (C: cue period; D: delay period; R: response period). From Funahashi et al. (1989), used with permission. (C) average firing rate during the delay period vs. cue location, for the neuron shown in (B). From Funahashi et al. (1989), used with permission. (D) Persistent activity of a cell in PFC of a monkey performing a delayed somatosensory discrimination task. Top panel: Rastergrams of a PFC cell arranged according to frequency of the base stimulus (indicated on the left). Middle panel: Trial averaged firing rate for several stimulus frequencies showing the monotonic response as a function of stimulus frequency. Bottom panel: Tuning curve of the cell in the delay period. From Romo et al. (1999), reprinted by permission from Nature, © 1989 Macmillan Publishers Ltd. The second example, shown in Figure 1B, presents a ‘spatial’ working memory task, the oculomotor-delayed-response (ODR) task (Funahashi et al., 1989, 1990, 1991) in which the animal is required to remember the location of a light spot on a screen during the delay interval, and respond at the end of the delay interval, making a saccade towards this location. Figure 1B shows rasters and trial averaged firing rate of a cell recorded in the PF cortex during the four phases of the task: in the first phase the monkey fixates a central spot on a screen; in the second phase a light spot at one of eight possible angles is presented (in this period the monkey continues to fixate the central spot); the third phase is the ‘delay period’ which starts with the removal of the stimulus and lasts for some seconds; finally, when the central spot disappears the monkey has to respond by making a saccade towards the location of the presented stimulus. Figure 1C shows the activity of the recorded cell during the delay period: this activity is maximal at a particular cue location (270°) and decreases away from that preferred location. This stimulus-selective, spatially tuned delay activity is observed for many of the recorded cells in PFC.\nOur last example is shown in Figure 1D. It represents a ‘parametric’ working memory task (Romo et al., 1999). In this task a monkey was trained to compare and discriminate the frequencies of two vibrotactile stimuli separated by a delay period. Figure 1D shows a cell in the inferior convexity that has persistent activity that varies monotonically with the cue frequency (indicated on the left and by the different curves)."}