Publications by category
Journal articles
Perry BAL, Mendez JC, Mitchell AS (2022). Cortico‐thalamocortical interactions for learning, memory and decision‐making. The Journal of Physiology, 601(1), 25-35.
Mendez JC, Perry BAL, Heppenstall RJ, Mason S, Mitchell AS (2022). Openness about animal research increases public support. Nature Neuroscience, 25(4), 401-403.
Mendoza G, Méndez JC, Pérez O, Prado L, Merchant H (2018). Neural basis for categorical boundaries in the primate pre-SMA during relative categorization of time intervals.
Nature Communications,
9(1).
Abstract:
Neural basis for categorical boundaries in the primate pre-SMA during relative categorization of time intervals
AbstractPerceptual categorization depends on the assignment of different stimuli to specific groups based, in principle, on the notion of flexible categorical boundaries. To determine the neural basis of categorical boundaries, we record the activity of pre-SMA neurons of monkeys executing an interval categorization task in which the limit between short and long categories changes between blocks of trials within a session. A large population of cells encodes this boundary by reaching a constant peak of activity close to the corresponding subjective limit. Notably, the time at which this peak is reached changes according to the categorical boundary of the current block, predicting the monkeys’ categorical decision on a trial-by-trial basis. In addition, pre-SMA cells also represent the category selected by the monkeys and the outcome of the decision. These results suggest that the pre-SMA adaptively encodes subjective duration boundaries between short and long durations and contains crucial neural information to categorize intervals and evaluate the outcome of such perceptual decisions.
Abstract.
Méndez JC, Rocchi L, Jahanshahi M, Rothwell J, Merchant H (2017). Probing the timing network: a continuous theta burst stimulation study of temporal categorization. Neuroscience, 356, 167-175.
Merchant H, Pérez O, Bartolo R, Méndez JC, Mendoza G, Gámez J, Yc K, Prado L (2015). Sensorimotor neural dynamics during isochronous tapping in the medial premotor cortex of the macaque. European Journal of Neuroscience, 41(5), 586-602.
Méndez JC, Pérez O, Prado L, Merchant H (2014). Linking Perception, Cognition, and Action: Psychophysical Observations and Neural Network Modelling. PLoS ONE, 9(7), e102553-e102553.
Mendez JC, Prado L, Mendoza G, Merchant H (2011). Temporal and Spatial Categorization in Human and Non-Human Primates. Frontiers in Integrative Neuroscience, 5
Zarco W, Merchant H, Prado L, Mendez JC (2009). Subsecond Timing in Primates: Comparison of Interval Production Between Human Subjects and Rhesus Monkeys.
Journal of Neurophysiology,
102(6), 3191-3202.
Abstract:
Subsecond Timing in Primates: Comparison of Interval Production Between Human Subjects and Rhesus Monkeys
This study describes the psychometric similarities and differences in motor timing performance between 20 human subjects and three rhesus monkeys during two timing production tasks. These tasks involved tapping on a push-button to produce the same set of intervals (range of 450 to 1,000 ms), but they differed in the number of intervals produced (single vs. multiple) and the modality of the stimuli (auditory vs. visual) used to define the time intervals. The data showed that for both primate species, variability increased as a function of the length of the produced target interval across tasks, a result in accordance with the scalar property. Interestingly, the temporal performance of rhesus monkeys was equivalent to that of human subjects during both the production of single intervals and the tapping synchronization to a metronome. Overall, however, human subjects were more accurate than monkeys and showed less timing variability. This was especially true during the self-pacing phase of the multiple interval production task, a behavior that may be related to complex temporal cognition, such as speech and music execution. In addition, the well-known human bias toward auditory as opposed to visual cues for the accurate execution of time intervals was not evident in rhesus monkeys. These findings validate the rhesus monkey as an appropriate model for the study of the neural basis of time production, but also suggest that the exquisite temporal abilities of humans, which peak in speech and music performance, are not all shared with macaques.
Abstract.
Graff-Guerrero A, De la Fuente-Sandoval C, Camarena B, Gómez-Martin D, Apiquián R, Fresán A, Aguilar A, Méndez-Núñez JC, Escalona-Huerta C, Drucker-Colín R, et al (2005). Frontal and limbic metabolic differences in subjects selected according to genetic variation of the SLC6A4 gene polymorphism.
Neuroimage,
25(4), 1197-1204.
Abstract:
Frontal and limbic metabolic differences in subjects selected according to genetic variation of the SLC6A4 gene polymorphism.
Allelic variants in the promoter region of the serotonin transporter (5-HTT) gene have been implicated in several psychiatric disorders and personality traits. In particular, two common alleles in a variable repeat sequence of the promoter region (SLC6A4) have been differentially associated with a display of abnormal levels of anxiety and affective illness in individuals carrying the "s" allele. The aim of this study was to compare the basal cerebral metabolic activity of non-psychiatric subjects in fronto-limbic structures to determine whether differences exist in basal metabolic activity within this functional polymorphism. PET scans with fluorine-18 fluorodeoxyglucose as radiotracer were performed in 71 non-psychiatric subjects previously screened for psychopathology and subsequently genotyped for SLC6A4; PET images were compared with SPM2 according to s/s (n = 27), s/l (n = 25), and l/l (n = 19) groups considering a significance threshold in a priori selected areas of P < 0.001 and an extent threshold > or =5 voxels. The analysis showed an effect of interest among the three genotype groups in right anterior cingulate gyrus (ACC), left middle frontal gyrus, and left posterior cingulate gyrus (PCC). Comparison between l/l vs. s/s showed increased metabolism for l/l in left middle frontal gyrus and an increase for s/s in right ACC and left PCC. Comparison between s/s vs. s/l showed an increase for s/s in left PCC and right ACC. Increased basal metabolism in fronto-limbic structures for the s/s group may be conceived as an "overactive metabolic state" of these structures, possibly related to an increased susceptibility for developing an anxiety-depression spectrum disorder.
Abstract.
Author URL.
Graff-Guerrero A, González-Olvera J, Fresán A, Gómez-Martín D, Méndez-Núñez JC, Pellicer F (2005). Repetitive transcranial magnetic stimulation of dorsolateral prefrontal cortex increases tolerance to human experimental pain.
Brain Res Cogn Brain Res,
25(1), 153-160.
Abstract:
Repetitive transcranial magnetic stimulation of dorsolateral prefrontal cortex increases tolerance to human experimental pain.
Dorsolateral prefrontal cortex (DLPFCx) has been implicated in pain perception and in a pain modulation pathway. However, the precise participation of this region is not completely understood. The aim of this study was to evaluate whether 1 Hz rTMS of DLPFCx modifies threshold and tolerance in experimental pain. The effect of 1 Hz rTMS during 15 min at 100% motor threshold was tested in one hundred and eighty right-handed healthy volunteers, using a parallel-group stimulation design. The stimulation sites were right or left DLPFCx, right or left motor cortex, vertex or sham. rTMS was applied in two experimental contexts: (1) to evaluate its transitory effect (interference or facilitation) during cold pressor threshold (CPTh) and tolerance (CPTt) and (2) to evaluate its long-term effect by stimulating before CPTh, CPTt, pain heat thermal threshold, pain pressure threshold and tolerance. During rTMS of right DLPFCx, an increase in left hand CPTt (mean +/- SD; 17.63 s +/- 5.58 to 30.94 s +/- 14.84, P < 0.001) and in right hand CPTt (18.65 s +/- 6.47 to 26.74 s +/- 11.85, P < 0.001) were shown. No other stimulation site modified any of the pain measures during or after rTMS. These results show that 1 Hz rTMS of right DLPFCx has a selective effect by increasing pain tolerance and also sustains a right hemisphere preference in pain processing.
Abstract.
Author URL.
Chapters
Merchant H, Bartolo R, Pérez O, Méndez JC, Mendoza G, Gámez J, Yc K, Prado L (2014). Neurophysiology of Timing in the Hundreds of Milliseconds: Multiple Layers of Neuronal Clocks in the Medial Premotor Areas. In (Ed) Advances in Experimental Medicine and Biology, Springer New York, 143-154.
Merchant H, Bartolo R, Méndez JC, Pérez O, Zarco W, Mendoza G (2011). What can be Inferred from Multiple-task Psychophysical Studies about the Mechanisms for Temporal Processing?. In (Ed) Multidisciplinary Aspects of Time and Time Perception, Springer Berlin Heidelberg, 207-229.
Merchant H, Naselaris T, Zarco W, Bartolo R, Prado L, Pérez O, Méndez JC (2008). Functional Architecture of Directional Tuning in the Primate Motor Cortex During 3D Reaching. In (Ed)
From Development to Degeneration and Regeneration of the Nervous System, Oxford University PressNew York, 243-264.
Abstract:
Functional Architecture of Directional Tuning in the Primate Motor Cortex During 3D Reaching
Abstract.
Publications by year
In Press
Rassi E, Zhang Y, Mendoza G, Mendez JC, Merchant H, Haegens S (In Press). Distinct beta frequencies reflect categorical decisions.
Abstract:
Distinct beta frequencies reflect categorical decisions
AbstractBeta oscillations are involved in a variety of cognitive functions beyond their traditional sensorimotor role. Based on prior findings of content-specific beta synchronization during working memory and decision making, we hypothesized that beta activity supports the activation and reactivation of cortical representations by mediating neural ensemble formation within and between brain regions. We here found that beta activity in monkey dorsolateral prefrontal cortex (dlPFC) and in pre-supplementary motor area (preSMA) reflects the content of a stimulus in relation to the task context, regardless of its objective properties. In multiple versions of a categorization task, we changed the boundary between categories from one block of trials to the next, such that a stimulus which belonged to one of two categories during one block could belong to the other category during the next one. During a delay in which monkeys had to hold their categorical decision in mind, we found that two distinct beta-band frequencies were consistently associated with the same two relative categories, and that activity in these respective bands predicted the animals’ responses. We characterized beta at these frequencies as transient bursts with distinct temporal profiles. We further showed that dlPFC and preSMA are connected via these distinct frequency channels, with dlPFC driving the frequency separation, a result supported by Granger causality and spike-field coherence analyses. In sum, these results provide support for the role of beta in forming neural ensembles, and further show that such ensembles synchronize at different beta frequencies.
Abstract.
2022
Perry BAL, Mendez JC, Mitchell AS (2022). Cortico‐thalamocortical interactions for learning, memory and decision‐making. The Journal of Physiology, 601(1), 25-35.
Mendez JC, Perry BAL, Heppenstall RJ, Mason S, Mitchell AS (2022). Openness about animal research increases public support. Nature Neuroscience, 25(4), 401-403.
2018
Mendoza G, Méndez JC, Pérez O, Prado L, Merchant H (2018). Neural basis for categorical boundaries in the primate pre-SMA during relative categorization of time intervals.
Nature Communications,
9(1).
Abstract:
Neural basis for categorical boundaries in the primate pre-SMA during relative categorization of time intervals
AbstractPerceptual categorization depends on the assignment of different stimuli to specific groups based, in principle, on the notion of flexible categorical boundaries. To determine the neural basis of categorical boundaries, we record the activity of pre-SMA neurons of monkeys executing an interval categorization task in which the limit between short and long categories changes between blocks of trials within a session. A large population of cells encodes this boundary by reaching a constant peak of activity close to the corresponding subjective limit. Notably, the time at which this peak is reached changes according to the categorical boundary of the current block, predicting the monkeys’ categorical decision on a trial-by-trial basis. In addition, pre-SMA cells also represent the category selected by the monkeys and the outcome of the decision. These results suggest that the pre-SMA adaptively encodes subjective duration boundaries between short and long durations and contains crucial neural information to categorize intervals and evaluate the outcome of such perceptual decisions.
Abstract.
2017
Méndez JC, Rocchi L, Jahanshahi M, Rothwell J, Merchant H (2017). Probing the timing network: a continuous theta burst stimulation study of temporal categorization. Neuroscience, 356, 167-175.
2015
Merchant H, Pérez O, Bartolo R, Méndez JC, Mendoza G, Gámez J, Yc K, Prado L (2015). Sensorimotor neural dynamics during isochronous tapping in the medial premotor cortex of the macaque. European Journal of Neuroscience, 41(5), 586-602.
2014
Méndez JC, Pérez O, Prado L, Merchant H (2014). Linking Perception, Cognition, and Action: Psychophysical Observations and Neural Network Modelling. PLoS ONE, 9(7), e102553-e102553.
Merchant H, Bartolo R, Pérez O, Méndez JC, Mendoza G, Gámez J, Yc K, Prado L (2014). Neurophysiology of Timing in the Hundreds of Milliseconds: Multiple Layers of Neuronal Clocks in the Medial Premotor Areas. In (Ed) Advances in Experimental Medicine and Biology, Springer New York, 143-154.
2011
Mendez JC, Prado L, Mendoza G, Merchant H (2011). Temporal and Spatial Categorization in Human and Non-Human Primates. Frontiers in Integrative Neuroscience, 5
Merchant H, Bartolo R, Méndez JC, Pérez O, Zarco W, Mendoza G (2011). What can be Inferred from Multiple-task Psychophysical Studies about the Mechanisms for Temporal Processing?. In (Ed) Multidisciplinary Aspects of Time and Time Perception, Springer Berlin Heidelberg, 207-229.
2009
Zarco W, Merchant H, Prado L, Mendez JC (2009). Subsecond Timing in Primates: Comparison of Interval Production Between Human Subjects and Rhesus Monkeys.
Journal of Neurophysiology,
102(6), 3191-3202.
Abstract:
Subsecond Timing in Primates: Comparison of Interval Production Between Human Subjects and Rhesus Monkeys
This study describes the psychometric similarities and differences in motor timing performance between 20 human subjects and three rhesus monkeys during two timing production tasks. These tasks involved tapping on a push-button to produce the same set of intervals (range of 450 to 1,000 ms), but they differed in the number of intervals produced (single vs. multiple) and the modality of the stimuli (auditory vs. visual) used to define the time intervals. The data showed that for both primate species, variability increased as a function of the length of the produced target interval across tasks, a result in accordance with the scalar property. Interestingly, the temporal performance of rhesus monkeys was equivalent to that of human subjects during both the production of single intervals and the tapping synchronization to a metronome. Overall, however, human subjects were more accurate than monkeys and showed less timing variability. This was especially true during the self-pacing phase of the multiple interval production task, a behavior that may be related to complex temporal cognition, such as speech and music execution. In addition, the well-known human bias toward auditory as opposed to visual cues for the accurate execution of time intervals was not evident in rhesus monkeys. These findings validate the rhesus monkey as an appropriate model for the study of the neural basis of time production, but also suggest that the exquisite temporal abilities of humans, which peak in speech and music performance, are not all shared with macaques.
Abstract.
2008
Merchant H, Naselaris T, Zarco W, Bartolo R, Prado L, Pérez O, Méndez JC (2008). Functional Architecture of Directional Tuning in the Primate Motor Cortex During 3D Reaching. In (Ed)
From Development to Degeneration and Regeneration of the Nervous System, Oxford University PressNew York, 243-264.
Abstract:
Functional Architecture of Directional Tuning in the Primate Motor Cortex During 3D Reaching
Abstract.
2005
Graff-Guerrero A, De la Fuente-Sandoval C, Camarena B, Gómez-Martin D, Apiquián R, Fresán A, Aguilar A, Méndez-Núñez JC, Escalona-Huerta C, Drucker-Colín R, et al (2005). Frontal and limbic metabolic differences in subjects selected according to genetic variation of the SLC6A4 gene polymorphism.
Neuroimage,
25(4), 1197-1204.
Abstract:
Frontal and limbic metabolic differences in subjects selected according to genetic variation of the SLC6A4 gene polymorphism.
Allelic variants in the promoter region of the serotonin transporter (5-HTT) gene have been implicated in several psychiatric disorders and personality traits. In particular, two common alleles in a variable repeat sequence of the promoter region (SLC6A4) have been differentially associated with a display of abnormal levels of anxiety and affective illness in individuals carrying the "s" allele. The aim of this study was to compare the basal cerebral metabolic activity of non-psychiatric subjects in fronto-limbic structures to determine whether differences exist in basal metabolic activity within this functional polymorphism. PET scans with fluorine-18 fluorodeoxyglucose as radiotracer were performed in 71 non-psychiatric subjects previously screened for psychopathology and subsequently genotyped for SLC6A4; PET images were compared with SPM2 according to s/s (n = 27), s/l (n = 25), and l/l (n = 19) groups considering a significance threshold in a priori selected areas of P < 0.001 and an extent threshold > or =5 voxels. The analysis showed an effect of interest among the three genotype groups in right anterior cingulate gyrus (ACC), left middle frontal gyrus, and left posterior cingulate gyrus (PCC). Comparison between l/l vs. s/s showed increased metabolism for l/l in left middle frontal gyrus and an increase for s/s in right ACC and left PCC. Comparison between s/s vs. s/l showed an increase for s/s in left PCC and right ACC. Increased basal metabolism in fronto-limbic structures for the s/s group may be conceived as an "overactive metabolic state" of these structures, possibly related to an increased susceptibility for developing an anxiety-depression spectrum disorder.
Abstract.
Author URL.
Graff-Guerrero A, González-Olvera J, Fresán A, Gómez-Martín D, Méndez-Núñez JC, Pellicer F (2005). Repetitive transcranial magnetic stimulation of dorsolateral prefrontal cortex increases tolerance to human experimental pain.
Brain Res Cogn Brain Res,
25(1), 153-160.
Abstract:
Repetitive transcranial magnetic stimulation of dorsolateral prefrontal cortex increases tolerance to human experimental pain.
Dorsolateral prefrontal cortex (DLPFCx) has been implicated in pain perception and in a pain modulation pathway. However, the precise participation of this region is not completely understood. The aim of this study was to evaluate whether 1 Hz rTMS of DLPFCx modifies threshold and tolerance in experimental pain. The effect of 1 Hz rTMS during 15 min at 100% motor threshold was tested in one hundred and eighty right-handed healthy volunteers, using a parallel-group stimulation design. The stimulation sites were right or left DLPFCx, right or left motor cortex, vertex or sham. rTMS was applied in two experimental contexts: (1) to evaluate its transitory effect (interference or facilitation) during cold pressor threshold (CPTh) and tolerance (CPTt) and (2) to evaluate its long-term effect by stimulating before CPTh, CPTt, pain heat thermal threshold, pain pressure threshold and tolerance. During rTMS of right DLPFCx, an increase in left hand CPTt (mean +/- SD; 17.63 s +/- 5.58 to 30.94 s +/- 14.84, P < 0.001) and in right hand CPTt (18.65 s +/- 6.47 to 26.74 s +/- 11.85, P < 0.001) were shown. No other stimulation site modified any of the pain measures during or after rTMS. These results show that 1 Hz rTMS of right DLPFCx has a selective effect by increasing pain tolerance and also sustains a right hemisphere preference in pain processing.
Abstract.
Author URL.