RESUMEN
Following the theoretical framework of coordinate and categorical principals for visuo-spatial processing, originally formulated by [Kosslyn, S. M. (1987). Seeing and imagining in the cerebral hemispheres: AQ computational approach. Psychological Review, 94, 148-175], we present data from an fMRI study on mental rotation, using the classic [Shepard, R. N., & Metzler, J. (1971). Mental rotation of three-dimensional objects. Science, 171, 701-703] task, comparing males and females. Subjects were presented with black-and-white drawings of 3-D shapes taken from the set of 3-D perspective drawings developed by [Shepard, R. N., & Metzler, J. (1971). Mental rotation of three-dimensional objects. Science, 171, 701-703], alternated with 2-D white bars as control stimuli. The drawings were presented pairwise, as black and white drawings against a black circular background. On half of the trials, the two 3-D shapes were congruent but portrayed with different orientation, in the other half the two shapes were incongruent. Analysis of response accuracy and reaction times did not reveal any significant differences between the sexes. However, clusters of significant neuronal activation were found in the superior parietal lobule (BA 7), more intensely over the right hemisphere, and bilaterally in the inferior frontal gyrus (BA 44/45). Males showed predominantly parietal activation, while the females, in addition, showed inferior frontal activation. We suggest that males may be biased towards a coordinate processing approach, and females biased towards a serial, categorical processing approach.
Asunto(s)
Imaginación/fisiología , Imagen por Resonancia Magnética , Percepción Espacial/fisiología , Percepción Visual/fisiología , Adulto , Femenino , Lateralidad Funcional/fisiología , Humanos , Procesamiento de Imagen Asistido por Computador , Masculino , Oxígeno/sangre , Estimulación Luminosa , Desempeño Psicomotor/fisiología , Tiempo de Reacción/fisiología , Caracteres SexualesRESUMEN
We hypothesized that brain activation during encoding and retrieval of visual material differed between epilepsy patients with hippocampal sclerosis (HS) and healthy controls. Eleven patients with epilepsy and HS and nine age- and education-matched control subjects were tested during functional MRI recording. A three-block design for visuospatial memory encoding and retrieval and an interference interval longer than 1 minute without memory tasks were used. All subjects revealed parietal, occipital, and prefrontal activation patterns during encoding. Interference revealed parietal more than occipital activation, whereas retrieval revealed asymmetrical frontal and parietal activation. Patients demonstrated a relative increase in occipitoparietal versus frontal cortical activation as compared with controls. Memory performance did not differ between patients and controls. The increased activation in occipitoparietal versus frontal areas in the patients suggests cortical reorganization of visuospatial recognition memory in epilepsy patients with HS. The study is limited by other factors that may contribute to the results, for example, antiepileptic drugs, effects of greater cognitive effort allocated in patients than controls, and possibly subclinical epileptic activity. However, normal visuospatial memory performance in our patients with HS suggests successful network plasticity.
Asunto(s)
Epilepsia del Lóbulo Temporal/fisiopatología , Lóbulo Frontal/fisiología , Hipocampo/patología , Recuerdo Mental/fisiología , Lóbulo Parietal/fisiología , Adulto , Epilepsia del Lóbulo Temporal/psicología , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Tiempo de Reacción , Percepción Espacial/fisiología , Percepción Visual/fisiologíaRESUMEN
We measured brain activation with functional magnetic resonance imaging (fMRI) while Finnish-Norwegian bilinguals silently translated sentences from Finnish into Norwegian and decided whether a later presented probe sentence was a correct translation of the original sentence. The control task included silent sentence reading and probe sentence decision within a single language, Finnish. The translation minus control task contrast activated the left inferior frontal gyrus (Brodmann's area 47) and the left basal ganglia. The left inferior frontal activation appears to be related to active semantic retrieval and the basal ganglia activation to a general action control function that works by suppressing competing responses.
Asunto(s)
Encéfalo/fisiología , Imagen por Resonancia Magnética , Multilingüismo , Semántica , Traducciones , Adulto , Ganglios Basales/fisiología , Mapeo Encefálico , Cerebelo/fisiología , Femenino , Finlandia , Lateralidad Funcional/fisiología , Humanos , Lenguaje , Masculino , Corteza Motora/fisiología , Noruega , Corteza Prefrontal/fisiología , Lectura , Lóbulo Temporal/fisiologíaRESUMEN
We investigated the effects of conflicting cues in visual attention on brain function, based on a modified version of the Posner cue-target paradigm. The classic paradigm utilizes either a peripheral or centrally placed cue that involuntary or voluntary results in a shift of attention to the cued side. The modified paradigm involves presenting both a peripheral and central cue at the same time, but where the two cues convey conflicting information regarding direction of attention. Functional magnetic resonance imaging (fMRI) were used to record neuronal activation in localized brain areas and networks when the subjects performed the attention task. We hypothesized that the 'exogenous invalid/endogenous valid' condition would activate the anterior attention system to a larger extent than the 'exogenous valid/endogenous invalid' condition, reflecting a need for top-down information processing in this condition. The results for performance data showed that the peripheral cue took precedence over the centrally placed cue when the two cues were in conflict, since reaction times were significantly longer in the "exogenous invalid/endogenous valid" condition. The fMRI data showed an increase in activation in the visual cortex, the left parietal lobule, and in the left cingulate gyrus in both the exogenous valid/endogenous invalid and exogenous invalid/endogenous valid conditions. For the exogenous invalid/endogenous valid condition, there were, in addition, significant activations also in the inferior and middle frontal gyri, and in the precentral gyrus. We interpret these findings as reflecting that these brain areas particularly involved in top-down modulation of attention that interferes with a bottom-up, exogenous-driven effect.
Asunto(s)
Atención/fisiología , Encéfalo/fisiología , Conflicto Psicológico , Señales (Psicología) , Adulto , Análisis de Varianza , Encéfalo/anatomía & histología , Encéfalo/irrigación sanguínea , Mapeo Encefálico , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Imagen por Resonancia Magnética/métodos , Masculino , Oxígeno/sangre , Tiempo de Reacción/fisiologíaRESUMEN
The present study used functional and structural MRI to investigate differences in neuronal substrates underlying shifts of attention in young and old subjects, studied with dichotic listening. Two different consonant-vowel syllables were presented and the subjects were instructed to attend to and report from either the left or right ear stimulus. Typically, a right-ear advantage is observed when attending to the right-ear stimulus, and a left-ear advantage when attending to the left-ear stimulus. The behavioral results showed that the old group had difficulties with attentional modulation of the right-ear advantage in the attend left condition. This is interpreted as a failure of an important aspect of attentional control; the top-down biasing of attention for selection of task-relevant stimulus. The fMRI results showed that an area in the left middle frontal gyrus was more activated in the young group compared to the old group in the attend left condition. The structural MRI data showed reduced gray matter density of the same area in the old group. Based on these converging findings, we suggest that the left middle frontal gyrus plays an important role in top-down biasing of selecting task-relevant stimuli, and to inhibit processing of task-irrelevant stimuli. To our knowledge, this is one of the first studies addressing the question on how age-related changes in attentional processing is reflected in both functional and structural differences in the brain.
Asunto(s)
Envejecimiento/fisiología , Mapeo Encefálico/métodos , Encéfalo/fisiología , Imagen por Resonancia Magnética/métodos , Adulto , Encéfalo/crecimiento & desarrollo , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
The aim of the present study was to investigate differences in brain activation in a family with SLI as compared to intact individuals with normally developed language during processing of language stimuli. Functional magnetic resonance imaging (fMRI) was used to monitor changes in neuronal activation in temporal and frontal lobe areas in 5 Finnish family members with specific language impairment (SLI) and 6 individuals in an intact control group. Magnetic resonance (MR) image acquisitions were made while the participants listened to series of isolated vowel sounds, pseudowords, and real words. The stimuli were digitized single Finnish vowel sounds, 3-phoneme pseudowords, and 3- and 4-phoneme real words. MR scanning was made with a 1.5 T Siemens Vision Plus scanner, and the auditory stimuli were presented according to an event-related fMRI design. The results showed significant differences between the family with SLI and the intact control group with regard to brain activation in areas in the temporal and frontal lobes. Temporal lobe activation differences were most pronounced in the middle temporal gyrus bordering the superior temporal sulcus. The control participants also activated an area in the inferior frontal lobe in BA 44. It is concluded that individuals with SLI showed reduced activation in brain areas that are critical for speech processing and phonological awareness. The present functional brain imaging data fit well with other recent imaging data that also showed structural abnormalities in the same and neighboring areas.
Asunto(s)
Familia , Lóbulo Frontal/fisiología , Trastornos del Lenguaje/fisiopatología , Imagen por Resonancia Magnética , Percepción del Habla/fisiología , Lóbulo Temporal/fisiología , Estimulación Acústica , Adolescente , Adulto , Anciano , Estudios de Casos y Controles , Niño , Análisis por Conglomerados , Femenino , Lóbulo Frontal/patología , Humanos , Trastornos del Lenguaje/genética , Imagen por Resonancia Magnética/métodos , Masculino , Persona de Mediana Edad , Linaje , Lóbulo Temporal/patologíaRESUMEN
OBJECTIVE: The authors used functional magnetic resonance imaging (fMRI) to investigate brain activation in patients with schizophrenia and major depression while they performed two tasks-a vigilance task and a mental arithmetic task-that differed in cognitive complexity. METHOD: In the vigilance task, the participants had to press a response button whenever a specific number was seen on a screen inside the MR scanner. In the mental arithmetic task, the participants had to add two consecutive numbers and press the response button whenever the sum was 10. fMRI was performed with a 1.5-T MR scanner. Twelve patients with recurrent nonpsychotic unipolar major depression, 12 patients with schizophrenia, and 12 healthy comparison subjects were included in the study. RESULTS: Performance data showed that the patients were impaired relative to the comparison subjects and showed no difference in performance between the patient groups. The patients with schizophrenia, but not those with major depression, had less activation in prefrontal brain regions, relative to the comparison participants. However, subtracting brain activation during the vigilance task from activation during the mental arithmetic task showed that the schizophrenia patients had activation in parietal areas. CONCLUSIONS: A double dissociation of parietal and frontal lobe activation was found for the schizophrenia patients and the depression patients. The greater parietal lobe activation in the patients with schizophrenia may reflect a compensatory strategy for the failure to recruit cognitive processes that involve frontal lobe areas when solving a mental arithmetic task.
Asunto(s)
Encéfalo/metabolismo , Trastornos del Conocimiento/etiología , Trastornos del Conocimiento/metabolismo , Trastorno Depresivo Mayor/metabolismo , Imagen por Resonancia Magnética , Pruebas Neuropsicológicas , Oxígeno/metabolismo , Esquizofrenia/metabolismo , Adulto , Encéfalo/anatomía & histología , Trastorno Depresivo Mayor/psicología , Femenino , Humanos , Masculino , Matemática , Oxígeno/sangre , Tiempo de Reacción , Esquizofrenia/complicaciones , Índice de Severidad de la EnfermedadRESUMEN
The present study used fMRI to investigate the relationship between stimulus presentation mode and attentional instruction in a free-report dichotic listening (DL) task with consonant-vowel (CV) syllables. Binaural and dichotic CV syllables were randomly presented to the subjects during four different instructional conditions: a passive listening instruction and three active instructions where subjects listened to both ears, right ear and left ear, respectively. The results showed that dichotic presentations activated areas in the superior temporal gyrus, middle and inferior frontal gyrus and the cingulate cortex to a larger extent than binaural presentations. Moreover, the results showed that increase of activation in these areas was differentially dependent on presentation mode and attentional instruction. Thus, it seems that speech perception, as studied with the DL procedure, involves a cortical network extending beyond primary speech perception areas in the brain, also including prefrontal cortex.
Asunto(s)
Pruebas de Audición Dicótica , Imagen por Resonancia Magnética , Corteza Prefrontal/fisiología , Percepción del Habla/fisiología , Adulto , Atención/fisiología , Vías Auditivas/fisiología , Mapeo Encefálico , Femenino , Lóbulo Frontal/fisiología , Giro del Cíngulo/fisiología , Humanos , Masculino , Red Nerviosa/fisiología , Fonética , Semántica , Lóbulo Temporal/fisiologíaRESUMEN
Focusing of attention to a specific speech source plays an important role in everyday speech perception. However, little is known of the neuronal substrates of focused attention in speech perception. Thus, the present study investigated the effects on neuronal activation of directed attention to auditory stimuli that differed in semantic content. Using an event-related fMRI protocol, single vowels, three-phoneme pseudowords and three- and four-phoneme real nouns and words were randomly presented to the subjects during four different instructional conditions. One condition was passive listening without any specific instructions of focusing of attention. The other conditions were attention focused on either the vowels, the pseudowords or the words. Thus, the acoustic stimulation was constant across conditions. The subjects were 13 healthy adults. Functional MRI was performed with a 1.5 T scanner, using an event-related design. During passive listening, there were significant activations bilaterally in the superior temporal gyrus. Instruction to attend to the pseudowords caused activation in middle temporal lobe areas, extending more anterior compared to the activations seen during passive listening. Instruction to attend to the vowel sounds caused an increase in activation in the superior/medial temporal lobe, with a leftward asymmetry. Instruction to attend to the words caused a leftward asymmetry, particularly in the middle and superior temporal gyri. It is concluded that attention plays a modulatory role in neuronal activation to speech sounds, producing specific activations to specific stimulus categories that may act to facilitate speech perception.