Mandy J. Maguire

Linking Brainwaves to the Brain: An ERP Primer

This article reviews literature on the characteristics and possible interpretations of the event-related potential (ERP) peaks commonly identified in research. The description of each peak includes typical latencies, cortical distributions, and possible brain sources of observed activity as well as the evoking paradigms and underlying psychological processes. The review is intended to serve as a tutorial for general readers interested in neuropsychological research and as a reference source for researchers using ERP techniques.

A developmental shift from similar to language-specific strategies in verb acquisition: a comparison of English, Spanish, and Japanese.

The worlds languages draw on a common set of event components for their verb systems. Yet, these components are differentially distributed across languages. At what age do children begin to use language-specific patterns to narrow possible verb meanings? English-, Japanese-, and Spanish-speaking adults, toddlers, and preschoolers were shown videos of an animated star performing a novel manner along a novel path paired with a language-appropriate nonsense verb. They were then asked to extend that verb to either the same manner or the same path as in training. Across languages, toddlers (2- and 2.5-year-olds) revealed a significant preference for interpreting the verb as a path verb. In preschool (3- and 5-year-olds) and adulthood, the participants displayed language-specific patterns of verb construal. These findings illuminate the way in which verb construal comes to reflect the properties of the input language.

Young Children Can Extend Motion Verbs to Point-Light Displays

In the first study using point-light displays (lights corresponding to the joints of the human body) to examine childrens understanding of verbs, 3-year-olds were tested to see if they could perceive familiar actions that corresponded to motion verbs (e.g., walking). Experiment 1 showed that children could extend familiar motion verbs (e.g., walking and dancing) to videotaped point-light actions shown in the intermodal preferential looking paradigm. Children watched the action that matched the requested verb significantly more than they watched the action that did not match the verb. In Experiment 2, the findings of Experiment 1 were validated by having children spontaneously produce verbs for these actions. The use of point-light displays may illuminate the factors that contribute to verb learning.

Neural substrates of semantic memory

Semantic memory is described as the storage of knowledge, concepts, and information that is common and relatively consistent across individuals (e.g., memory of what is a cup). These memories are stored in multiple sensorimotor modalities and cognitive systems throughout the brain (e.g., how a cup is held and manipulated, the texture of a cups surface, its shape, its function, that is related to beverages such as coffee, and so on). Our ability to engage in purposeful interactions with our environment is dependent on the ability to understand the meaning and significance of the objects and actions around us that are stored in semantic memory. Theories of the neural basis of the semantic memory of objects have produced sophisticated models that have incorporated to varying degrees the results of cognitive and neural investigations. The models are grouped into those that are (1) cognitive models, where the neural data are used to reveal dissociations in semantic memory after a brain lesion occurs; (2) models that incorporate both cognitive and neuroanatomical information; and (3) models that use cognitive, neuroanatomic, and neurophysiological data. This review highlights the advances and issues that have emerged from these models and points to future directions that provide opportunities to extend these models. The models of object memory generally describe how category and/or feature representations encode for object memory, and the semantic operations engaged in object processing. The incorporation of data derived from multiple modalities of investigation can lead to detailed neural specifications of semantic memory organization. The addition of neurophysiological data can potentially provide further elaboration of models to include semantic neural mechanisms. Future directions should incorporate available and newly developed techniques to better inform the neural underpinning of semantic memory models.

EEG theta and alpha responses reveal qualitative differences in processing taxonomic versus thematic semantic relationships.

Despite the importance of semantic relationships to our understanding of semantic knowledge, the nature of the neural processes underlying these abilities are not well understood. In order to investigate these processes, 20 healthy adults listened to thematically related (e.g., leash-dog), taxonomically related (e.g., horse-dog), or unrelated (e.g., desk-dog) noun pairs as their EEG was recorded. The data were analyzed using both event-related potentials (ERP) and event-related spectral perturbation (ERSP) analyses. The spatiotemporal ERP and ERSP results were analyzed further with principal component analysis (PCA). When comparing unrelated to related word pairs, the expected N400 effect was confirmed, as well as differences in theta and alpha oscillations. When comparing thematically and taxonomically related word pairs, the ERP revealed no significant differences, but the ERSP did. Specifically, theta power increased over right frontal areas for thematic versus taxonomic relationships and alpha power increased over parietal areas for taxonomic versus thematic relationships. The different oscillatory patterns over different brain regions suggest that thematic and taxonomic relationships engage distinct neural processes. Specifically, thematic relationships engage memory processes, while taxonomic relationships may require additional inhibitory or attention processes.

The influence of perceptual and semantic categorization on inhibitory processing as measured by the N2–P3 response

In daily activities, humans must attend and respond to a range of important items and inhibit and not respond to unimportant distractions. Our current understanding of these processes is largely based on perceptually simple stimuli. This study investigates the interaction of conceptual-semantic categorization and inhibitory processing using Event Related Potentials (ERPs). Participants completed three Go-NoGo tasks that increased systematically in the degree of conceptual-semantic information necessary to respond correctly (from single items to categories of objects and animals). Findings indicate that the N2 response reflects inhibitory processing but does not change significantly with task difficulty. The P3 NoGo amplitude, on the other hand, is attenuated by task difficulty. Further, the latency of the peak of the P3 NoGo response elicited by the most difficult task is significantly later than are the peaks detected during performance of the other two tasks. Thus, the level of complexity of conceptual-semantic representations influences inhibitory processing in a systematic way. This inhibition paradigm may be a key for investigating inhibitory dysfunction in patient populations.

Semantic memory retrieval circuit: role of pre-SMA, caudate, and thalamus.

We propose that pre-supplementary motor area (pre-SMA)-thalamic interactions govern processes fundamental to semantic retrieval of an integrated object memory. At the onset of semantic retrieval, pre-SMA initiates electrical interactions between multiple cortical regions associated with semantic memory subsystems encodings as indexed by an increase in theta-band EEG power. This starts between 100-150 ms after stimulus presentation and is sustained throughout the task. We posit that this activity represents initiation of the object memory search, which continues in searching for an object memory. When the correct memory is retrieved, there is a high beta-band EEG power increase, which reflects communication between pre-SMA and thalamus, designates the end of the search process and resultant in object retrieval from multiple semantic memory subsystems. This high beta signal is also detected in cortical regions. This circuit is modulated by the caudate nuclei to facilitate correct and suppress incorrect target memories.

An fMRI investigation of cognitive stages in reasoning by analogy

We compared reasoning about four-term analogy problems in the format (A:B::C: D) to semantic and perceptual control conditions that required matching without analogical mapping. We investigated distinct phases of the problem solving process divided into encoding, mapping/inference, and response. Using fMRI, we assessed the brain activation relevant to each of these phases with an emphasis on achieving a better understanding of analogical reasoning relative to these other matching conditions. We predicted that the analogical condition would involve the most cognitive effort in the encoding and mapping/inference phases, while the control conditions were expected to engage greater prefrontal cortex (PFC) activation at the response period. Results showed greater activation for the analogical condition relative to the control conditions at the encoding phase in several predominantly left lateralized and medial areas of the PFC. Similar results were observed for the mapping/inference phase, though this difference was limited to the left PFC and rostral PFC. The response phase resulted in the fastest and most accurate responses in the analogy condition relative to the control conditions. This was accompanied by greater processing within the left lateral and the medial PFC for the control conditions relative to the analogy condition, consistent with most of the cognitive processing of the analogy condition having occurred in the prior task phases. Overall we demonstrate that the left ventral and dorsal lateral, medial, and rostral PFC are important in both the encoding of relational information, mapping and inference processes, and verification of semantic and perceptual responses in four term analogical reasoning.

Frontal theta and alpha power and coherence changes are modulated by semantic complexity in Go/NoGo tasks

To study the interactions between semantic processing and motor response inhibition, we recorded scalp EEG as subjects performed a series of Go/NoGo response inhibition tasks whose response criteria depended on different levels of semantic processing. Three different tasks were used. The first required the subject to make a Go/NoGo decision based on pictures of one particular car or one particular dog. The second used pictures of different types of cars and of dogs, and the final task used stimuli that ranged across multiple types of objects and animals. We found that the theta-band EEG power recorded during the NoGo response was attenuated as a function of semantic complexity while the peak latency was delayed in only the most complex category task. Further, frontal alpha-band desynchronization was strongest for the simplest task and remained close to baseline for the other tasks. Finally, there was significant theta-band coherence between the frontal pole and pre-SMA for the NoGo conditions across tasks, which was not found in the Go trials. These findings provide information about how more rostral frontal regions interact with the pre-SMA during response inhibition across different stimuli and task demands: specifically, level of processing affects latency, difficulty affects amplitude, and coherence is affected by whether the decision is Go or NoGo.

How Semantic Categorization Influences Inhibitory Processing in Middle-Childhood: An Event Related Potentials study.

Throughout middle-childhood, inhibitory processes, which underlie many higher order cognitive tasks, are developing. Little is known about how inhibitory processes change as a task becomes conceptually more difficult during these important years. In adults, as Go/NoGo tasks become more difficult there is a systematic decrease in the P3NoGo response, indicating the use of effective inhibitory strategies (Maguire et al., 2009). This paper investigates the age at which children employ similar inhibitory strategies by studying behavioral and Event Related Potential (ERP) measures of response inhibition for three Go/NoGo tasks. Seventeen 7-8 year-olds and twenty 10-11-year-olds completed three Go/NoGo tasks that differed in the level of categorization necessary to respond. Both age groups displayed slower reaction times as the tasks became more difficult. Further, both groups displayed the predicted Go vs. NoGo P3 amplitude differences in the two simplest tasks, but no significant P3 differences for the most complex task. The reason for this pattern of responses was different in the different age groups. Similar to adults in previous work, the oldest children showed an attenuation of the P3 NoGo response with task difficulty, and no corresponding changes in the Go amplitude. The younger children displayed the opposite pattern, a significant increase in the Go amplitude with task difficulty, and no changes in the NoGo response. These response patterns indicate that efficient inhibitory strategies are developing throughout middle-childhood.