title: An ERP N400 study: Semantic processing across modalities in the human brain

authors: Perry, Sarah

subjects: ERP

abstract: Semantic processing in the brain of both language and action has been associated with the N400; an event-related potential (ERP) that is typically present when information has violated one’s semantic expectations. We know that the brain receives and processes information from multiple modalities which means that cross-modal semantic processing is more aligned with how semantic processing is likely to occur in comparison to unimodal semantic processing. The N400 is a consistent effect across cross-modal language-based studies. But we know that the topographical distribution of the N400 does vary between language-based and non-language-based paradigms. Therefore, to investigate cross-modal semantic processing within the action domain, we presented participants with photographs portraying the implementation of common actions. These sequences concluded with a sound that was either congruent or incongruent with the prior action photographs. In our ERP study of 25 participants, with a mean age of 23 years (SD = 10.78 years), we¹ found an N400 effect for incongruent information processing. In addition, our findings showed a delayed N400 effect and a reduced P200 amplitude for incongruent information. These results suggest that cross-modal semantic processing of action sequences requires an increased cognitive workload which is evidenced when semantic processing does not progress as expected. Considered as a whole, these results indicate that cross-modal semantic processing is similar to unimodal processing. Cross-modal information likely requires the involvement of additional cognitive processes that are not present during unimodal paradigms.

text: An ERP N400 study: Semantic processing across modalities in the human brain Semantic processing in the brain of both language and action has been associated with the N400; an event-related potential (ERP) that is typically present when information has violated one’s semantic expectations. We know that the brain receives and processes information from multiple modalities which means that cross-modal semantic processing is more aligned with how semantic processing is likely to occur in comparison to unimodal semantic processing. The N400 is a consistent effect across cross-modal language-based studies. But we know that the topographical distribution of the N400 does vary between language-based and non-language-based paradigms. Therefore, to investigate cross-modal semantic processing within the action domain, we presented participants with photographs portraying the implementation of common actions. These sequences concluded with a sound that was either congruent or incongruent with the prior action photographs. In our ERP study of 25 participants, with a mean age of 23 years (SD = 10.78 years), we¹ found an N400 effect for incongruent information processing. In addition, our findings showed a delayed N400 effect and a reduced P200 amplitude for incongruent information. These results suggest that cross-modal semantic processing of action sequences requires an increased cognitive workload which is evidenced when semantic processing does not progress as expected. Considered as a whole, these results indicate that cross-modal semantic processing is similar to unimodal processing. Cross-modal information likely requires the involvement of additional cognitive processes that are not present during unimodal paradigms.

year: 2023

title: Concurrent schedule performance of possums: a comparison of two models

authors: Bron, Angela

abstract: These experiments examined the behaviour of brushtail possums (Trichosurus vulpecula) under concurrent variable-interval schedules of reinforcement. In the first experiment the lever pressing of six possums resulted in intermittent access to a barley/carob mixture under four pairs of variable-interval schedules. In most respects, the behaviour of the possums was similar to that observed with other species. However, the degree of undermatching of the response ratios to the obtained reinforcement-rate ratios was greater than is normally observed with these schedules. Both the Generalised Matching Law and the Contingency-Discriminability model described the data well, although, where overmatching was obtained, the parameter values given by the Contingency-Discriminability model did not make sense in terms of the original assumptions of the model. The second experiment examined the possibility that the undermatching related to the length of the changeover delay used. Six possums were exposed to five different pairs of concurrent schedules at each of four different changeover-delay lengths (ranging from 0 to 6 s). Time allocation and post-changeover delay responses more closely approximated matching with a 2-s changeover delay than with a 0-s delay, but no further changes in sensitivity were observed with further increases in changeover-delay length. Overmatching was consistently observed in the post changeover delay data, resulting in un-interpretable parameter values from Contingency-Discriminability analyses. The addition of the punishment parameter (w) to the Contingency-Discriminability model, suggested to deal with such data, did not generally result in more sensible parameter estimates. The third experiment attempted to bias possums responding using qualitatively different reinforcers. Equal variable-interval schedules were used with the barley/carob mixture available on one schedule and Cocopopsᵀᴹ or coconut on the other. Possums’ behaviour was biased by these foods, with a small bias away from the barley/carob mixture resulting from the Cocopops and a large bias towards the barley/carob mixture resulting from the coconut. In the fourth experiment, graded point estimates of bias were obtained by presenting four different concentrations of salted barley/carob mixture (ranging from 0% to 6%) on one schedule and plain barley/carob mixture on the other schedule. Small biases were found with 0% and 2% salt, and large biases were found towards the barley/carob mixture with 4% and 6% salt. To assess whether bias remains constant with changes in the reinforcer-rate ratio, further conditions were conducted with 4% and 6% salt, with four pairs of unequal concurrent variable-interval schedules. Analyses of these data with both the Generalised Matching Law and the Contingency-Discriminability Model revealed an interaction between bias and the reinforcement-rate ratio. This interaction may be due to an improvement in discriminability due to the different reinforcers. The behaviour of the possums was generally well described by both the Generalised Matching Law and the Contingency-Discriminability model. Overall, neither model was better at describing behaviour under the above conditions, although several problems were found with the application of the Contingency-Discriminability model.

text: Concurrent schedule performance of possums: a comparison of two models These experiments examined the behaviour of brushtail possums (Trichosurus vulpecula) under concurrent variable-interval schedules of reinforcement. In the first experiment the lever pressing of six possums resulted in intermittent access to a barley/carob mixture under four pairs of variable-interval schedules. In most respects, the behaviour of the possums was similar to that observed with other species. However, the degree of undermatching of the response ratios to the obtained reinforcement-rate ratios was greater than is normally observed with these schedules. Both the Generalised Matching Law and the Contingency-Discriminability model described the data well, although, where overmatching was obtained, the parameter values given by the Contingency-Discriminability model did not make sense in terms of the original assumptions of the model. The second experiment examined the possibility that the undermatching related to the length of the changeover delay used. Six possums were exposed to five different pairs of concurrent schedules at each of four different changeover-delay lengths (ranging from 0 to 6 s). Time allocation and post-changeover delay responses more closely approximated matching with a 2-s changeover delay than with a 0-s delay, but no further changes in sensitivity were observed with further increases in changeover-delay length. Overmatching was consistently observed in the post changeover delay data, resulting in un-interpretable parameter values from Contingency-Discriminability analyses. The addition of the punishment parameter (w) to the Contingency-Discriminability model, suggested to deal with such data, did not generally result in more sensible parameter estimates. The third experiment attempted to bias possums responding using qualitatively different reinforcers. Equal variable-interval schedules were used with the barley/carob mixture available on one schedule and Cocopopsᵀᴹ or coconut on the other. Possums’ behaviour was biased by these foods, with a small bias away from the barley/carob mixture resulting from the Cocopops and a large bias towards the barley/carob mixture resulting from the coconut. In the fourth experiment, graded point estimates of bias were obtained by presenting four different concentrations of salted barley/carob mixture (ranging from 0% to 6%) on one schedule and plain barley/carob mixture on the other schedule. Small biases were found with 0% and 2% salt, and large biases were found towards the barley/carob mixture with 4% and 6% salt. To assess whether bias remains constant with changes in the reinforcer-rate ratio, further conditions were conducted with 4% and 6% salt, with four pairs of unequal concurrent variable-interval schedules. Analyses of these data with both the Generalised Matching Law and the Contingency-Discriminability Model revealed an interaction between bias and the reinforcement-rate ratio. This interaction may be due to an improvement in discriminability due to the different reinforcers. The behaviour of the possums was generally well described by both the Generalised Matching Law and the Contingency-Discriminability model. Overall, neither model was better at describing behaviour under the above conditions, although several problems were found with the application of the Contingency-Discriminability model.

year: 2001

title: Evaluation of iwi and hapū participation in the resource consents processes of six district councils

authors: Backhurst, Michael

subjects: New Zealand

abstract: This working paper analyses the processes adopted by councils for involving hapū/iwi in plan implementation, including the resource consents process. Three topic issues were investigated to assess plan implementation — urban amenity, storm water, and issues of importance to iwi. Questions were asked about the capacity of hapū/iwi to engage in the resource consent process, which resource issues were of concern to them, their relationship with council and consent applicants, and their perception of the consent process. Most resources listed in the questionnaire were of concern to hapū/iwi, with water quality, wāhi tapu and heritage the most commonly cited. In conclusion, we found a general dissatisfaction on the part of hapū/iwi with councils’ performance with respect to both Treaty relationships and consent processing under the RMA. A further contributing factor to the poor relationships found between hapū/iwi and councils, was the lack of clarity over the role of hapū and iwi in resource management. In several districts, diverging responses from hapū/iwi and councils to questions about level of understanding and commitment suggests there is a need for more effective communication. These problems are compounded by the generally low capacity of hapū/iwi to participate in resource consent processes. These findings suggest that there is much to be done to improve relationships and behaviour of these key stakeholder groups in the plan implementation process if key provisions in the RMA related to hapū/iwi interests are to be fulfilled. The differences shown in reciprocal perceptions have serious implications for establishing a sound working partnership between councils and hapū/iwi in their areas. Making clear these discrepancies is a first step towards taking the measures needed for building a better partnership. Further, the capacity of hapū/iwi to participate could be better utilised if there was greater integration between regional and district councils on issues of significance and processes for iwi involvement.

text: Evaluation of iwi and hapū participation in the resource consents processes of six district councils This working paper analyses the processes adopted by councils for involving hapū/iwi in plan implementation, including the resource consents process. Three topic issues were investigated to assess plan implementation — urban amenity, storm water, and issues of importance to iwi. Questions were asked about the capacity of hapū/iwi to engage in the resource consent process, which resource issues were of concern to them, their relationship with council and consent applicants, and their perception of the consent process. Most resources listed in the questionnaire were of concern to hapū/iwi, with water quality, wāhi tapu and heritage the most commonly cited. In conclusion, we found a general dissatisfaction on the part of hapū/iwi with councils’ performance with respect to both Treaty relationships and consent processing under the RMA. A further contributing factor to the poor relationships found between hapū/iwi and councils, was the lack of clarity over the role of hapū and iwi in resource management. In several districts, diverging responses from hapū/iwi and councils to questions about level of understanding and commitment suggests there is a need for more effective communication. These problems are compounded by the generally low capacity of hapū/iwi to participate in resource consent processes. These findings suggest that there is much to be done to improve relationships and behaviour of these key stakeholder groups in the plan implementation process if key provisions in the RMA related to hapū/iwi interests are to be fulfilled. The differences shown in reciprocal perceptions have serious implications for establishing a sound working partnership between councils and hapū/iwi in their areas. Making clear these discrepancies is a first step towards taking the measures needed for building a better partnership. Further, the capacity of hapū/iwi to participate could be better utilised if there was greater integration between regional and district councils on issues of significance and processes for iwi involvement.

year: 2004-03