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P Rämä

Publications and source records attributed to P Rämä.

16 recordsLinked to original sources
PubMed2001

Working memory of identification of emotional vocal expressions: an fMRI study.

The distribution of brain activation during working memory processing of emotional vocal expressions was studied using functional magnetic resonance imaging (fMRI) in eight female subjects performing n-back tasks with three load levels (0-back, 1-back, and 2-back tasks). The stimuli in the n-back tasks were the Finnish female name [Saara] uttered in an astonished, angry, frightened, commanding, and scornful mode, and the subjects were instructed to memorize the emotional connotation of the stimuli. Subregions in the prefrontal, parietal, and visual association areas were load-dependently activated during the performance of the n-back tasks. The most consistently activated areas in the prefrontal region were detected in the inferior frontal gyrus corresponding to Brodmann's areas (BAs) 44 and 45 and in the middle and superior frontal gyri (BAs 6/8). Activation was also found in the inferior parietal lobe and intraparietal sulcus (BAs 40/7) and visual association areas including the lingual and fusiform gyri. The results suggest that a distributed neuronal network in occipital, parietal, and frontal areas is involved in working memory processing of emotional content of aurally presented information.

Adult↗
PubMed2001

Dissociation of the neural systems for working memory maintenance of verbal and nonspatial visual information.

Working memory for names and faces was investigated to ascertain whether verbal and nonspatial visual information is maintained in working memory by separate neural systems. The subjects performed a delayed match-to-sample task for famous or unfamous faces and names and a sensorimotor control task. Several occipital, temporal, parietal, and prefrontal areas were activated during all memory delays, in comparison with the control delays. Greater delay activity for unfamous faces than for names was obtained in the right fusiform gyrus, right inferior frontal gyrus (IFG), right IFG/precentral gyrus, and right medial superior frontal gyrus, whereas greater delay activity for unfamous names than for faces was observed in the precuneus, left insula/postcentral gyrus, and left IFG/precentral gyrus. There was no significant difference in the prefrontal activity in the comparison between famous faces and names. Greater delay activity for famous names than for faces was obtained in visual association and parietal areas. The results indicate that there is a functional dissociation based on information type within the neural system that is responsible for working memory maintenance of verbal and nonspatial visual information.

Adult↗
PubMed2000

Modulation of slow brain potentials by working memory load in spatial and nonspatial auditory tasks.

Slow event-related brain potentials were recorded from the human scalp during spatial and nonspatial auditory delayed matching-to-sample and n-back tasks to find out whether there are differences in the distribution of slow potentials during the retention of audiospatial and pitch information. The performance of both the location and pitch tasks produced slow potentials during the delay phase of the memory tasks. The delay-related slow potential was modulated by the amount of information to be processed during the tasks at the parietal-occipital sites. The distribution of mnemonic modulation was, however, not different between the tasks. The results suggest that there is integration of auditory information processing in the neuronal networks engaged in mnemonic processing of pitch and location.

Adolescent↗
PubMed2000

Working memory of auditory localization.

To investigate brain mechanisms of sound location memory, we studied the distribution of brain activation with functional magnetic resonance imaging (fMRI) in subjects performing an audiospatial n-back task with three memory load levels. Working memory processing of audiospatial information activated areas in the superior, middle and inferior frontal gyri, and in the posterior parietal and middle temporal cortices. In a control experiment, fMRI during audio- and visuospatial 2-back task performances revealed only few differentially activated subregions between the two tasks. These results demonstrate that working memory processing of auditory locations involves a distributed network of brain areas and suggest that mnemonic processing of audio- and visuospatial information is directed along a common neural pathway in the posterior parietal and prefrontal cortices.

Acoustic Stimulation↗
PubMed1999

Selective interference reveals dissociation between auditory memory for location and pitch.

Effects of interfering task-irrelevant tones varying in location or pitch on auditory location and pitch n-back tasks were investigated to study whether there is segregation of spatial and non-spatial information processing in the auditory working memory. The subjects performed spatial and non-spatial auditory 1- and 2-back tasks with and without location or pitch interference. In the 1-back tasks, location but not pitch interference significantly impaired location task performance whereas pitch but not location interference disrupted pitch task performance. In the 2-back tasks, neither the location nor the pitch task performance was differentially disrupted by the distractors, suggesting that there is memory load-dependent segregation in the handling of location and pitch information in the neuronal networks engaged in auditory working memory.

Acoustic Stimulation↗
PubMed1999

Selective interference reveals dissociation between memory for location and colour.

The aim was to study whether there is indication of a dissociation in processing of visuospatial and colour information in working memory in humans. Experimental subjects performed visuospatial and colour n-back tasks with and without visuospatial and colour distractive stimuli presented in the middle of the delay period to specifically affect mnemonic processing of task-related information. In the high memory-load condition, the visuospatial, but not the colour, task was selectively disrupted by visuospatial but not colour distractors. When subvocal rehearsal of the memoranda in the colour task was prevented by articulatory suppression; colour task performance was also selectively disrupted by distractors qualitatively similar to the memoranda. The results support the suggestion that visual working memory for location is processed separate from that for colour.

Adult↗
PubMed1998

Distribution of cortical activation during visuospatial n-back tasks as revealed by functional magnetic resonance imaging.

Human neuroimaging studies conducted during visuospatial working memory tasks have inconsistently detected activation in the prefrontal cortical areas depending presumably on the type of memory and control tasks employed. We used functional magnetic resonance imaging to study brain activation related to the performance of a visuospatial n-back task with different memory loads (0-back, 1-back and 2-back tasks). Comparison of the 2-back versus 0-back tasks revealed consistent, bilateral activation in the medial frontal gyrus (MFG), superior frontal sulcus and adjacent cortical tissue (SFS/SFG) in all subjects and in six out of seven subjects in the intraparietal sulcus (IPS). Activation was also detected in the inferior frontal gyrus, medially in the superior frontal gyrus, precentral gyrus, superior and inferior parietal lobuli, occipital visual association areas, anterior and posterior cingulate areas and in the insula. Comparison between the 1-back versus 0-back tasks revealed activation only in a few brain areas. Activation in the MFG, SFS/SFG and IPS appeared dependent on memory load. The results suggest that the performance of a visuospatial working memory task engages a network of distributed brain areas and that areas in the dorsal visual pathway are engaged in mnemonic processing of visuospatial information.

Adolescent↗
PubMed1997

Effects of music and white noise on working memory performance in monkeys.

It has been suggested that Mozart's music may have beneficial effects on the performance of cognitive tasks in humans. In the present study the effects of Mozart's piano music, white noise, simple rhythm and silence were studied on the performance of a delayed response (DR) task in monkeys. The acoustic treatments were given for 15 min, either before or during DR testing. The acoustic treatments did not affect DR performance when given before testing. However, Mozart's piano music played during DR testing caused a significant deterioration in the performance of the monkeys, whereas white noise improved it. It is suggested that Mozart's music serves as distractive stimulation during DR performance thus affecting working-memory-related neuronal processing and performance. White background noise, on the other hand, may improve DR performance by protecting against environmental distraction during testing.

Acoustic Stimulation↗
PubMed1997

Visuospatial mnemonic load modulates event-related slow potentials.

Electroencephalographic slow wave potentials were recorded during the performance of visuospatial working memory tasks. The aim was to study the effects of varying mnemonic loads on slow potentials, and to dissociate the contribution of mnemonic and motor components. Subjects were tested with three spatial delayed matching-to-sample tasks in which the mnemonic load varied while the preparatory motor demands remained constant. The delay-related slow potential was more negative during the tasks in which the subjects had to memorize the locations of six or four stimuli than when only one location had to be memorized. Significant differences between the slow potentials in the tasks with different mnemonic loads were recorded at frontal and temporal recording sites. Since the preparatory motor requirements were similar in all tasks, the modulation of slow potentials reflects working memory processing rather than motor preparatory activity.

Adolescent↗
PubMed1997

The effects of alpha-2 agonist, medetomidine and its antagonist, atipamezole on reaction and movement times in a visual choice reaction time task in monkeys.

Alpha-2 adrenoceptor agonists have been shown to improve the working memory task performance of aged monkeys. Suggestions offered to explain this finding include improved short-term memory processing, slight sedation, and decreased distractiveness. Although sedation is evident at high doses, it may also contribute to the working memory task performance at low doses. The aim of the present work was to find out whether the positive effects of an alpha-2 agonist, medetomidine, on working memory performance could be explained by its sedative effects. This was accomplished by measuring the reaction and movement times of monkeys performing a visual choice reaction time task under the influence of medetomidine or its antagonist atipamezole. In the task a trial began with the monkey holding a central pad. After a short period one of two lateral light emitting diodes was turned on for 300 ms and the monkeys were trained to release the central bar and touch either of the bars, situated below the diodes, depending on the location of the stimulus. The reaction and movement times were significantly longer than on saline control only at the highest dose of medetomidine (10.0 micrograms/kg). At the lowest dose of atipamezole (0.01 mg/kg), the reaction times were significantly shorter than on saline control. The results of this study demonstrate that low doses of medetomidine, which have earlier been shown to improve working memory performance, do not induce sedation as measured by reaction and movement times.

Adrenergic alpha-Agonists↗
PubMed1997

Dissociation of mnemonic coding and other functional neuronal processing in the monkey prefrontal cortex.

Single-neuron activity was recorded in the prefrontal cortex of three monkeys during the performance of a spatial delayed alternation (DA) task and during the presentation of a variety of visual, auditory, and somatosensory stimuli. The aim was to study the relationship between mnemonic neuronal processing and other functional neuronal responsiveness at the single-neuron level in the prefrontal cortex. Recordings were performed in both experimental situations from 152 neurons. The majority of the neurons (92%) was recorded in the prefrontal cortex. Nine of the neurons were recorded in the dorsal bank of the anterior cingulate sulcus and two in the premotor cortex. Of the total number of neurons recorded in the prefrontal area, 32% fired in relation to the DA task performance and 39% were responsive to sensory stimulation or to the movements of the monkey outside of the memory task context. Altogether 42% of the recorded neurons were neither activated by the various stimuli nor by the DA task performance. Three types of task-related neuronal activity were recorded: delay related, delay and movement related, and movement related. The majority of the task-related neurons (n = 33, 73%) fired in relation to the delay period. Of the delay-related neurons, 26 (79%) were spatially selective. The number of spatially selective delay-related neurons of the whole population of recorded neurons was 18%. Twelve task-related neurons (27%) fired in relation to the response period of the DA task. Five of these neurons changed their firing rate during the delay period and were classified as delay/movement-related neurons. Contrary to the delay-related neurons, less than half (42%) of the response-related neurons were spatially selective. The majority (70%) of the delay-related neurons could not be activated by any of the sensory stimuli used and did not fire in relation to the movements of the monkey. The remaining portion of the delay-related neurons was activated by stationary and moving visual stimuli or by visual fixation of an object. In contrast to the delay-related neurons, the majority (66%) of the task-related neurons firing in relation to the movement period were also responsive to sensory stimulation outside of the task context. The majority of these neurons responded to visual stimulation, visual fixation of an object, or tracking eye movements. One neuron gave a somatomotor and another a polysensory response. The majority (n = 37, 67%) of all neurons responding to stimulation outside of the task context did not fire in relation to the DA task performance. The majority of their responses was elicited by visual stimuli or was related to visual fixation of an object or to eye movements. Only six neurons fired in relation to auditory, somatosensory, or somatomotor stimulation. This study provides further evidence about the significance of the dorsolateral prefrontal cortex in spatial working memory processing. Although a considerable number of all DA task-related neurons responded to visual, somatosensory, and auditory stimulation or to the movements of the monkey, most delay-related neurons engaged in the spatial DA task did not respond to extrinsic sensory stimulation. These results indicate that most prefrontal neurons firing selectively during the delay phase of the DA task are highly specialized and process only task-related information.

Animals↗
PubMed1996

The effects of prefrontal intracortical microinjections of an alpha-2 agonist, alpha-2 antagonist and lidocaine on the delayed alternation performance of aged rats.

A selective alpha-2 agonist medetomidine, a selective alpha-2 antagonist atipamezole and lidocaine were injected into the prefrontal cortex of aged rats that had been trained to perform a delayed alternation (DA) task in a T maze. Medetomidine at the dose of 0.01 microgram/microliter improved the memory task performance in four of five rats. The fifth rat improved its performance at the dose of 1.0 microgram/microliter. Atipamezole did not have any effect on the task performance. The effect of a systemic dose of medetomidine (3 micrograms/kg), which was previously shown to improve the task performance in old rats, was reversed by an intracortical injection of atipamezole. Lidocaine impaired the DA performance significantly. The results suggest that the beneficial effects of medetomidine on the working memory of old rats are mediated at least partly through the prefrontal cortex.

Adrenergic alpha-Agonists↗
PubMed1996

Medetomidine, atipamezole, and guanfacine in delayed response performance of aged monkeys.

The effects of a highly selective alpha-2 adrenergic agonist medetomidine and its antagonist atipamezole were studied on the delayed response task performance of aged monkeys. Medetomidine, at the dose of 1.0 micrograms/kg, improved the memory task performance, whereas atipamezole had no effect on the performance at any dose. It has earlier been shown that alpha-2 adrenergic agonists clonidine and guanfacine improve age-associated memory impairment, but also contradictory effects of clonidine have been reported. There is evidence that the ability of alpha-2 agonists to improve DR task performance is due to its selective action on the alpha-2A receptor subtype. Clonidine and medetomidine are much less selective than guanfacine with respect to alpha-2A and alpha-2B receptor subtypes. Therefore, we also studied the effect of guanfacine on the memory task performance of the same aged monkeys in the same testing conditions to compare the effectiveness of these two alpha-2 adrenergic compounds. Guanfacine improved memory task performance at the dose of 0.0001 mg/kg. The results indicate that alpha-2 agonists, independent of their different selectivity with respect to alpha-2A/2B receptor subtypes, are beneficial drugs in improving the performance in the delayed response task.

Adrenergic alpha-Agonists↗
PubMed1995

A spatial oculomotor memory-task performance produces a task-related slow shift in human electroencephalography.

Electroencephalographic (EEG) deflections in humans related to the performance of memory-guided saccades were studied in this work. The EEG deflections were recorded during 2 spatial oculomotor delayed response tasks in which the subject was instructed to make a saccade either to the right or to the left depending on the spatial location of the cue which had been shown in the beginning of the delay period. The EEG deflections were compared to those recorded during a control task in which the subject also made a saccade to the right or to the left after a delay but the requirement to keep spatial information actively in mind was minimized. A slow delay-related shift was recorded during all task conditions. The slow shift was positive in the most frontal and negative in the more posterior recording sites. The negative slow shift in the more posterior recording sites was larger in the memory tasks than in the control task. Since the memory and the control tasks differed mainly in their requirement to hold spatial information in mind it is suggested that the difference in the magnitude of slow shifts between the memory and the control tasks reflects neural activity related to spatial working memory. But although the oculomotor responses in all tasks were similar, the preparatory activities for the impending eye movements may not have been similar and in addition to working memory may have contributed to the observed differences in the slow shifts.

Adult↗
PubMed1992

Effects of medetomidine, an alpha-2 adrenoceptor agonist, and atipamezole, an alpha-2 antagonist, on spatial memory performance in adult and aged rats.

The effects of a novel, highly selective alpha-2 agonist, medetomidine, and its antagonist, atipamezole, were studied on the working memory of rats performing a spatial delayed alternation task. Testing was performed in two stages, at the age of 8.3 months (mean) and again when the rats were 17.6 months (mean). A low dose (3 micrograms/kg) and a high dose (30 micrograms/kg) of medetomidine improved the performance of the old rats in the memory task but had no effect on the young rats. The dose-response curve of medetomidine resembles that of guanfacine, another alpha-2 agonist. At the low dose of medetomidine (3 micrograms/kg) the animals showed no signs of sedation. Since medetomidine even at a low dose has a beneficial effect on the memory performance of old rats, it could be a good candidate for the treatment of age-associated memory dysfunction.

Adrenergic alpha-Agonists↗