Biomedical subjects

C A Seger

Publications and source records attributed to C A Seger.

8 recordsLinked to original sources

PubMed2000

Hemispheric asymmetries and individual differences in visual concept learning as measured by functional MRI.

Dynamic changes in brain regions active while learning novel visual concepts were examined in humans using functional magnetic resonance imaging. Participants learned to distinguish between exemplars of two categories, formed as distortions of different unseen prototype stimuli. Regions of the right hemisphere (dorsolateral prefrontal and inferior parietal areas) were active early in learning and throughout task performance, whereas homologous portions of the left hemisphere were active only in later stages of learning. Left dorsolateral prefrontal activation was found only in participants who showed superior conceptual learning. Such a progression from initial right-hemisphere processing of specific instances to bilateral activity as left-hemisphere conceptual processes are recruited may underlie the development of many forms of visual knowledge.

Adult↗

PubMed2000

Functional magnetic resonance imaging evidence for right-hemisphere involvement in processing unusual semantic relationships.

Brain areas active in generating usual (typical) or unusual (atypical) noun-verb relations were examined using functional magnetic resonance imaging. Seven adults generated the 1st verb to come to mind (usual verb) in response to novel and repeated nouns (priming test) and then generated either an unusual verb or the 1st verb to come to mind in response to novel nouns (unusual test). The left inferior prefrontal cortex (LIPC) and right cerebellum were more active when generating usual verbs to novel nouns than to repeated nouns. When participants generated unusual verbs, there was no increased activation in LIPC, but there was increased activity in the right middle and superior frontal gyri, left middle frontal gyrus, and bilateral cerebellum. Results support theories that the right hemisphere is involved in the processing of distant associations that may be useful in creative thought and problem solving.

Adult↗

PubMed1999

Verb generation priming involves conceptual implicit memory.

Brain activation patterns differ and generation latencies are reduced when generating verbs to repeated nouns (Raichle et al., 1994). Amnesic participants show normal magnitude of priming (Seger et al., 1997). Despite its importance in neuropsychology, verb generation priming is not well characterized psychologically. Six behavioral studies found that verb generation priming was specific to the verb rather than to the noun or the noun-verb pair, was equivalent after overt or covert generation and after reading verbs or generating verbs, was affected by levels of processing, and transferred completely across languages in bilinguals. These results indicate that verb generation priming involves priming of particular responses and happens at a conceptual level. These findings provide new insights about the significance of brain imaging and neuropsychological studies involving verb generation priming.

Analysis of Variance↗

PubMed1999

Striatal activation during acquisition of a cognitive skill.

The striatum is thought to play an essential role in the acquisition of a wide range of motor, perceptual, and cognitive skills, but neuroimaging has not yet demonstrated striatal activation during nonmotor skill learning. Functional magnetic resonance imaging was performed while participants learned probabilistic classification, a cognitive task known to rely on procedural memory early in learning and declarative memory later in learning. Multiple brain regions were active during probabilistic classification compared with a perceptual-motor control task, including bilateral frontal cortices, occipital cortex, and the right caudate nucleus in the striatum. The left hippocampus was less active bilaterally during probabilistic classification than during the control task, and the time course of this hippocampal deactivation paralleled the expected involvement of medial temporal structures based on behavioral studies of amnesic patients. Findings provide initial evidence for the role of frontostriatal systems in normal cognitive skill learning.

Adult↗

PubMed1998

Independent judgment-linked and motor-linked forms of artificial grammar learning.

Three experiments investigated whether a motor-linked measure (string typing speed) and an judgment-linked measure (grammatical judgment of strings) accessed the same implicit learning mechanisms in the artificial grammar learning task. Participants first studied grammatical strings through observation or through responding to each letter by typing it and then performed typing and grammatical judgment tests. Grammatical judgment test performance was better after observation than after respond learning, whereas typing test performance on higher order relations was worse after observation than after respond learning (Experiment 1). Participants transferred grammatical knowledge across letter sets on the grammatical judgment test, but not on the typing test (Experiment 2). Typing speed did not differ for hits (grammatical strings classified by participants as grammatical) and misses (grammatical strings classified as nongrammatical, Experiment 3). These results are consistent with typing and grammatical judgment tests tapping independent mechanisms and indicate that implicit learning may consist of many different forms of learning rather than being a unitary learning mechanism.

Adolescent↗

PubMed1997

Two forms of sequential implicit learning.

A serial reaction time (SRT) experiment tested the hypothesis that there are two independent forms of implicit learning: learning that is linked to making judgments about stimuli, and learning that is linked to motor processing. Participants performed 2, 6, or 12 blocks of single task SRT, dual task SRT, or observation with one of five sequence; each sequence had the same underlying structure. Participants then performed two implicit tests, SRT (a motor-linked test) and pattern judgment, as well as a generation test and an explicit knowledge test. There was a double dissociation of the effect of sequence surface structure on SRT and pattern judgment. SRT and pattern judgment competence developed independently of each other across length of acquisition task. Performance on both implicit tasks did not depend on explicit knowledge. These results indicate that the SRT and pattern judgment measures tap independent forms of implicit learning, which is consistent with the modular nature of memory and cognition.

Adult↗

PubMed1997

Preserved verb generation priming in global amnesia.

In the verb generation task, participants are presented with nouns and generate for each one an appropriate verb. Raichle et al. (Cerebral Cortex, 1994, 4, 8-26) found that when participants generated verbs to repeated nouns, generation latencies were reduced and different patterns of brain activation were present. In order to examine whether verb generation priming is dependent or independent of declarative memory, verb generation priming was compared between 13 amnesic (seven with alcoholic Korsakoff's syndrome, six with other etiologies) and 19 control participants (10 with a history of alcoholism). Both amnesic and control participants became faster across blocks on repeated nouns and slowed when novel nouns were introduced. Priming was verb specific for both groups: it was equivalent whether generated to a repeated or a novel noun. Verb generation priming, therefore, can occur independently of declarative memory.

Adult↗

PubMed1994

Implicit learning.

Implicit learning is nonepisodic learning of complex information in an incidental manner, without awareness of what has been learned. Implicit learning experiments use 3 different stimulus structures (visual, sequence, and function) and 3 different dependent measures or response modalities (conceptual fluency, efficiency, and prediction and control). Implicit learning may require a certain minimal amount of attention and may depend on attentional and working memory mechanisms. The result of implicit learning is implicit knowledge in the form of abstract (but possibly instantiated) representations rather than verbatim or aggregate representations. Implicit learning shows biases and dissociations in learning different stimulus structures. The dependence of implicit learning on particular brain areas is discussed, some conclusions are drawn for modeling implicit learning, and the interaction of implicit and explicit learning is considered.

Concept Formation↗