- Email: [email protected]
The functional relevance of visual cortex for symbolic action priming
Abstracts In conclusion, our results suggest that PPC play a crucial role in the generation of the Simon effect, i.e.: processing the irrelevant spatial information. This information commonly interferes with the selection of the hand to perform the correct response in the Simon task. Single-pulse TMS, applied 100 ms after stimulus onset on the right PPC, produced a reduction of the effect: this result can be interpreted as a disruption of the representation of the irrelevant spatial information.
rTMS Poster Only 212
Anterior temporal lobes and non-verbal semantic processing:
Pobric G1, Jefferies E2, Ralph A Lambon1, 1The University of Manchester (Manchester, UK); 2University of York (York, UK) Objective: The representation of semantic knowledge in the human brain remains controversial, as many theories regard distributed brain regions along the connections between them as neural basis of semantic memory (Warrignton and McCarthy, 1994; Shallice, 1988; Martin, 2007). By contrast unified conceptual representation theories argue that the neural network requires a shared hub in anterior temporal lobes (ATL) that supports the interactive activation in all modalities and all semantic categories (Patterson et al., 2007; Rogers et al., 2004; Rogers and McClelland, 2004). It is critically important, therefore, to derive convergent evidence from diverse techniques about the nature of semantic representations in the ATL regions. To elucidate this debate, we used offline, low-frequency, repetitive transcranial magnetic stimulation (rTMS) to disrupt neural processing temporarily in the left and right ATL during semantic association task. Method: In the study, the participants’ performance on the semantic tasks (timed word and picture associations) and the control task (timed scrambled word/picture judgment) was compared with and without 10 minutes of offline 1Hz rTMS (600 pulses) over the left temporal pole (MNI: -53, 4, -32), right temporal pole (MNI: 52, 2, -28) and middle parietal-occipital junction (POz) as a control site. Result: The time required to make semantic association was slowed considerably, yet specifically, by this procedure for both left and right temporal poles, affecting words and pictures to the same degree, while rTMS delivered at control site had no impact. The results confirm that both temporal poles form a critical substrate within the neural network that supports conceptual knowledge independent of modality. Conclusion: The aim of this study was to demonstrate that ATL regions are critically important in the representation and activation of semantic memory. By temporarily interfering with the verbal and non verbal semantic processing in neurologically intact participants we were able to demonstrate for the first time that anterior temporal lobes, bilaterally, are the core neural substrate for the formation of semantic representations. We did not find hemispheric differences in processing pictures and words. This lack of double dissociation previously reported in patients can be explained by true amodal nature of anterior temporal lobes.
307 TMS-induced disruption of perception (2;3). Here, we tested whether symbolic action priming also remains intact despite TMS-induced visual masking of the prime. Method: We applied single-pulse transcranial magnetic stimulation (spTMS) over primary visual cortex during the behaviorally controlled execution of a combined visual masking and symbolic action priming paradigm (1). Stimuli consisted of two sequentially presented arrows. Depending on instruction, subjects were either required to identify and respond to the first, i.e., prime arrow, or to indicate the second arrow’s orientation (see Fig. 1). By varying the prime-TMS SOA over trials, we were able to determine the exact time point at which disruption of primary visual cortex interfered with conscious recognition of the prime and/or with its behavioral priming effect on the subsequent visual target. Results: Repeated-measures ANOVA revealed that performance in both tasks significantly deteriorated during V1 TMS at a prime-TMS SOA of 80ms. Hence, both conscious prime recognition and target priming were disrupted at the same temporal stage. We also revealed that these effects only occurred for those stimulus locations within the visual field whose retinotopic position was targeted by TMS. Conclusion: Our results fit other TMS studies finding a visual suppression of conscious perception at the 80-100ms time window (4:5), which is thought to represent the ‘‘feedforward sweep’’ of visual processing. Furthermore, the lack of a task-specific TMS effect implies that subliminal action priming, as conscious visual awareness, relies on a neural pathway employing striate cortex at the identical temporal stage. Contradicting earlier claims that visual information circumvents V1 during subliminal priming, our data suggest that symbolic action priming relies on an intact retinogeniculo-striate pathway. 1. Vorberg et al., PNAS, 003 2. Boyer et al., PNAS, 2005 3. Ro et al., Neuropsychologia, 2008 4. Amassian et al., Electroencephalogr Clin Neurophysiol, 1989 5. Corthout et al., Neuroreport, 2000
TMS
Imaging
Poster Only
Poster Only
213
214
The functional relevance of visual cortex for symbolic action priming
Brain activation that is modulated by the level of the integrity of corticospinal system in Multiple Sclerosis patients
Jacobs C1, van der Mark S2, Schuhmann T1, Schwarzbach J3, Goebel R1, Sack AT1, 1Maastricht University (Maastricht, NL); 2University Children’s Hospital (Zu¨rich, CH); 3Trento University (Rovereto, IT)
Steens A, de Vries A, van der Hoeven JH, Heersema DJ, Heerings MAP, Maurits NM, Renken RJ, Zijdewind I, University Medical Center Groningen (Groningen, NL)
Objective: Psychophysical evidence suggests that subliminal visual stimuli can exert subsequent behavioral effects (1). Recent TMS studies demonstrated that some features of a visual stimulus can still be processed despite
Objective: In patients suffering from multiple sclerosis (MS), progressive axonal demyelination leads to a decline in muscle activation. Compensatory mechanisms in the motor system may become effective to diminish
rTMS Poster Only 212
Anterior temporal lobes and non-verbal semantic processing:
Pobric G1, Jefferies E2, Ralph A Lambon1, 1The University of Manchester (Manchester, UK); 2University of York (York, UK) Objective: The representation of semantic knowledge in the human brain remains controversial, as many theories regard distributed brain regions along the connections between them as neural basis of semantic memory (Warrignton and McCarthy, 1994; Shallice, 1988; Martin, 2007). By contrast unified conceptual representation theories argue that the neural network requires a shared hub in anterior temporal lobes (ATL) that supports the interactive activation in all modalities and all semantic categories (Patterson et al., 2007; Rogers et al., 2004; Rogers and McClelland, 2004). It is critically important, therefore, to derive convergent evidence from diverse techniques about the nature of semantic representations in the ATL regions. To elucidate this debate, we used offline, low-frequency, repetitive transcranial magnetic stimulation (rTMS) to disrupt neural processing temporarily in the left and right ATL during semantic association task. Method: In the study, the participants’ performance on the semantic tasks (timed word and picture associations) and the control task (timed scrambled word/picture judgment) was compared with and without 10 minutes of offline 1Hz rTMS (600 pulses) over the left temporal pole (MNI: -53, 4, -32), right temporal pole (MNI: 52, 2, -28) and middle parietal-occipital junction (POz) as a control site. Result: The time required to make semantic association was slowed considerably, yet specifically, by this procedure for both left and right temporal poles, affecting words and pictures to the same degree, while rTMS delivered at control site had no impact. The results confirm that both temporal poles form a critical substrate within the neural network that supports conceptual knowledge independent of modality. Conclusion: The aim of this study was to demonstrate that ATL regions are critically important in the representation and activation of semantic memory. By temporarily interfering with the verbal and non verbal semantic processing in neurologically intact participants we were able to demonstrate for the first time that anterior temporal lobes, bilaterally, are the core neural substrate for the formation of semantic representations. We did not find hemispheric differences in processing pictures and words. This lack of double dissociation previously reported in patients can be explained by true amodal nature of anterior temporal lobes.
307 TMS-induced disruption of perception (2;3). Here, we tested whether symbolic action priming also remains intact despite TMS-induced visual masking of the prime. Method: We applied single-pulse transcranial magnetic stimulation (spTMS) over primary visual cortex during the behaviorally controlled execution of a combined visual masking and symbolic action priming paradigm (1). Stimuli consisted of two sequentially presented arrows. Depending on instruction, subjects were either required to identify and respond to the first, i.e., prime arrow, or to indicate the second arrow’s orientation (see Fig. 1). By varying the prime-TMS SOA over trials, we were able to determine the exact time point at which disruption of primary visual cortex interfered with conscious recognition of the prime and/or with its behavioral priming effect on the subsequent visual target. Results: Repeated-measures ANOVA revealed that performance in both tasks significantly deteriorated during V1 TMS at a prime-TMS SOA of 80ms. Hence, both conscious prime recognition and target priming were disrupted at the same temporal stage. We also revealed that these effects only occurred for those stimulus locations within the visual field whose retinotopic position was targeted by TMS. Conclusion: Our results fit other TMS studies finding a visual suppression of conscious perception at the 80-100ms time window (4:5), which is thought to represent the ‘‘feedforward sweep’’ of visual processing. Furthermore, the lack of a task-specific TMS effect implies that subliminal action priming, as conscious visual awareness, relies on a neural pathway employing striate cortex at the identical temporal stage. Contradicting earlier claims that visual information circumvents V1 during subliminal priming, our data suggest that symbolic action priming relies on an intact retinogeniculo-striate pathway. 1. Vorberg et al., PNAS, 003 2. Boyer et al., PNAS, 2005 3. Ro et al., Neuropsychologia, 2008 4. Amassian et al., Electroencephalogr Clin Neurophysiol, 1989 5. Corthout et al., Neuroreport, 2000
TMS
Imaging
Poster Only
Poster Only
213
214
The functional relevance of visual cortex for symbolic action priming
Brain activation that is modulated by the level of the integrity of corticospinal system in Multiple Sclerosis patients
Jacobs C1, van der Mark S2, Schuhmann T1, Schwarzbach J3, Goebel R1, Sack AT1, 1Maastricht University (Maastricht, NL); 2University Children’s Hospital (Zu¨rich, CH); 3Trento University (Rovereto, IT)
Steens A, de Vries A, van der Hoeven JH, Heersema DJ, Heerings MAP, Maurits NM, Renken RJ, Zijdewind I, University Medical Center Groningen (Groningen, NL)
Objective: Psychophysical evidence suggests that subliminal visual stimuli can exert subsequent behavioral effects (1). Recent TMS studies demonstrated that some features of a visual stimulus can still be processed despite
Objective: In patients suffering from multiple sclerosis (MS), progressive axonal demyelination leads to a decline in muscle activation. Compensatory mechanisms in the motor system may become effective to diminish