Biomedical subjects

Jerome N Sanes

Publications and source records attributed to Jerome N Sanes.

6 recordsLinked to original sources

PubMed2005

Movement quantity and frequency coding in human motor areas.

Studies of movement coding have indicated a relationship between functional MRI signals and increasing frequency of movement in primary motor cortex and other motor-related structures. However, prior work has typically used block-designs and fixed-time intervals across the varying movements frequencies that may prevent ready distinction of brain mechanisms related to movement quantity and, especially, movement frequency. Here, we obtained functional MRI signals from humans working in an event-related design to extract independent activation related to movement quantity or movement frequency. Participants tapped once, twice, or thrice at 1, 2, or 3 Hz, and the tapping evoked activation related to movement quantity in the precentral and postcentral gyri, supplementary motor area, cerebellum, putamen, and thalamus. Increasing movement frequency failed to yield activation in these motor-related areas, although linear movement frequency affects occurred in nonmotor regions of cortex and subcortex. Our results do not replicate prior data suggesting movement frequency encoding in motor-related areas; instead we observed movement quantity coding in motor-related brain areas. The discrepancy between prior studies and this study likely relates to methodology concerns. We suggest that the movement quantity relationships in human motor areas and encoding of movement frequency in nonmotor areas may reflect a functional anatomical substrate for mediating distinct movement parameters.

Adult↗

PubMed2003

Experience-dependent activation patterns in human brain during visual-motor associative learning.

Multiple brain regions, including parietal and frontal cortical areas, seem to participate in learning and rehearsing associations between spatially defined visual cues and appropriate motor responses. However, because most previous studies have related learning to changes in brain activation according to elapsed time or number of trials but not categories based on performance, it remains unclear how and when areas implicated in learning sensory-motor associations actually participate in the process. The current experiment used functional magnetic resonance imaging to examine changes in brain activation when participants learned to associate an arbitrarily located visual cue with a finger movement. Associative trials were categorized as incorrect, first correct, or subsequent correct. Participants also performed a spatially compatible visual-motor control task. A group analysis revealed four major findings addressing the behavioral processes occurring during forming and rehearsing visual-motor rules. First, brain networks related to processing associative information, through initial learning to rehearsal, yielded more activation in a myriad of neocortical structures than did a simple motor task. Second, we revealed frontal and parietal areas that differentially processed errors and correct responses. Third, we found frontal-parietal networks that seemed to mediate the transition of learning to rehearsing arbitrary visual-motor associations and that this activation exhibited dynamic characteristics. Last, we found a frontal-parietal network that appeared to have a key role in expressing the learned sensory-motor association. The current results provide a foundation for understanding how neocortical structures participate in the various behavioral processes that combine to form and consolidate novel and arbitrary sensory-motor associations.

Adult↗

PubMed2003

Motor "binding:" do functional assemblies in primary motor cortex have a role?

In this issue of Neuron, Jackson and colleagues describe a functional correlate of neural synchrony related to movement control. Synchrony strength in cortico-motoneuronal output neurons in primary motor cortex depended upon similarity of these neurons' connectivity pattern with the spinal cord. These results could form the foundation for subsequent investigations of motor binding.

Animals↗

PubMed2003

Neocortical mechanisms in motor learning.

The ability to learn novel motor skills has fundamental importance for adaptive behavior. Neocortical mechanisms support human motor skill learning, from simple practice to adaptation and arbitrary sensory-motor associations. Behavioral and neural manifestations of motor learning evolve in time and involve multiple structures across the neocortex. Modifications of neural properties, synchrony and synaptic efficacy are all related to the development and maintenance of motor skill.

Animals↗

PubMed2002

Cognitive mechanisms of transitive inference.

We examined how the brain organizes interrelated facts during learning and how the facts are subsequently manipulated in a transitive inference (TI) paradigm (e.g., if A<B and B<C, then A<C). This task determined features such as learned facts and behavioral goals, but the learned facts could be organized in any of several ways. For example, if one learns a list by operating on paired items, the pairs may be stored individually as separate facts and reaction time (RT) should decrease with learning. Alternatively, the pairs may be stored as a single, unified list, which may yield a different RT pattern. We characterized RT patterns that occurred as participants learned, by trial and error, the predetermined order of 11 shapes. The task goal was to choose the shape occurring closer to the end of the list, and feedback about correctness was provided during this phase. RT increased even as its variance decreased during learning, suggesting that the learnt knowledge became progressively unified into a single representation, requiring more time to manipulate as participants acquired relational knowledge. After learning, non-adjacent (NA) list items were presented to examine how participants reasoned in a TI task. The task goal also required choosing from each presented pair the item occurring closer to the list end, but without feedback. Participants could solve the TI problems by applying formal logic to the previously learnt pairs of adjacent items; alternatively, they could manipulate a single, unified representation of the list. Shorter RT occurred for NA pairs having more intervening items, supporting the hypothesis that humans employ unified mental representations during TI. The response pattern does not support mental logic solutions of applying inference rules sequentially, which would predict longer RT with more intervening items. We conclude that the brain organizes information in such a way that reflects the relations among the items, even if the facts were learned in an arbitrary order, and that this representation is subsequently used to make inferences.

Adolescent↗

PubMed2002

Frontal and parietal lobe activation during transitive inference in humans.

Cortical areas engaged in knowledge manipulation during reasoning were identified with functional magnetic resonance imaging (MRI) while participants performed transitive inference (TI) on an ordered list of 11 items (e.g. if A < B and B < C, then A < C). Initially, participants learned a list of arbitrarily ordered visual shapes. Learning occurred by exposure to pairs of list items that were adjacent in the sequence. Subsequently, functional MR images were acquired as participants performed TI on non-adjacent sequence items. Control tasks consisted of height comparisons (HT) and passive viewing (VIS). Comparison of the TI task with the HT task identified activation resulting from TI, termed 'reasoning', while controlling for rule application, decision processes, perception, and movement, collectively termed 'support processes'. The HT-VIS comparison revealed activation related to support processes. The TI reasoning network included bilateral prefrontal cortex (PFC), pre-supplementary motor area (preSMA), premotor area (PMA), insula, precuneus, and lateral posterior parietal cortex. By contrast, cortical regions activated by support processes included the bilateral supplementary motor area (SMA), primary motor cortex (M1), somatic sensory cortices, and right PMA. These results emphasize the role of a prefrontal-parietal network in manipulating information to form new knowledge based on familiar facts. The findings also demonstrate PFC activation beyond short-term memory to include mental operations associated with reasoning.

Adult↗