Papers by Maurício de Jesus Dias Martins
Topics in Cognitive Science, 2019
In many domains of human cognition, hierarchically structured representations are thought to play... more In many domains of human cognition, hierarchically structured representations are thought to play a key role. In this paper, we start with some foundational definitions of key phenomena like "sequence" and "hierarchy," and then outline potential signatures of hierarchical structure that can be observed in behavioral and neuroimaging data. Appropriate behavioral methods include classic ones from psycholinguistics along with some from the more recent artificial grammar learning and sentence processing literature. We then turn to neuroimaging evidence for hierarchical structure with a focus on the functional MRI literature. We conclude that, although a broad consensus exists about a role for a neural circuit incorporating the inferior frontal gyrus, the superior temporal sulcus, and the arcuate fasciculus, considerable uncertainty remains about the precise computational function(s) Correspondence should be sent to Julia Udd en,
Brain Structure and Function, 2020
The ability to generate complex hierarchical structures is a crucial component of human cognition... more The ability to generate complex hierarchical structures is a crucial component of human cognition which can be expressed in the musical domain in the form of hierarchical melodic relations. The neural underpinnings of this ability have been investigated by comparing the perception of well-formed melodies with unexpected sequences of tones. However, these contrasts do not target specifically the representation of rules generating hierarchical structure. Here, we present a novel paradigm in which identical melodic sequences are generated in four steps, according to three different rules: The Recursive rule, generating new hierarchical levels at each step; The Iterative rule, adding tones within a fixed hierarchical level without generating new levels; and a control rule that simply repeats the third step. Using fMRI, we compared brain activity across these rules when participants are imagining the fourth step after listening to the third (generation phase), and when participants listened to a fourth step (test sound phase), either well-formed or a violation. We found that, in comparison with Repetition and Iteration, imagining the fourth step using the Recursive rule activated the superior temporal gyrus (STG). During the test sound phase, we found fronto-temporo-parietal activity and hippocampal de-activation when processing violations, but no differences between rules. STG activation during the generation phase suggests that generating new hierarchical levels from previous steps might rely on retrieving appropriate melodic hierarchy schemas. Previous findings highlighting the role of hippocampus and inferior frontal gyrus may reflect processing of unexpected melodic sequences, rather than hierarchy generation per se.
Human Brain Mapping, 2019
Generation of hierarchical structures, such as the embedding of subordinate elements into larger ... more Generation of hierarchical structures, such as the embedding of subordinate elements into larger structures, is a core feature of human cognition. Processing of hierarchies is thought to rely on lateral prefrontal cortex (PFC). However, the neural underpinnings supporting active generation of new hierarchical levels remain poorly understood. Here, we created a new motor paradigm to isolate this active generative process by means of fMRI. Participants planned and executed identical movement sequences by using different rules: a Recursive hierarchical embedding rule, generating new hierarchical levels; an Iterative rule linearly adding items to existing hierarchical levels, without generating new levels; and a Repetition condition tapping into short term memory, without a transformation rule. We found that planning involving generation of new hierarchical levels (Recursive condition vs. both Iterative and Repetition) activated a bilateral motor imagery network, including cortical and subcortical structures. No evidence was found for lateral PFC involvement in the generation of new hierarchical levels. Activity in basal ganglia persisted through execution of the motor sequences in the contrast Recursive versus Iteration, but also Repetition versus Iteration, suggesting a role of these structures in motor short term memory. These results showed that the motor network is involved in the generation of new hierarchical levels during motor sequence planning, while lateral PFC activity was neither robust nor specific. We hypothesize that lateral PFC might be important to parse hierarchical sequences in a multi-domain fashion but not to generate new hierarchical levels. K E Y W O R D S fMRI, hierarchy, motor, prefrontal cortex, recursion
Brain, 2019
The generation of hierarchical structures is central to language, music and complex action. Under... more The generation of hierarchical structures is central to language, music and complex action. Understanding this capacity and its potential impairments requires mapping its underlying cognitive processes to the respective neuronal underpinnings. In language, left inferior frontal gyrus and left posterior temporal cortex (superior temporal sulcus/middle temporal gyrus) are considered hubs for syntactic processing. However, it is unclear whether these regions support computations specific to language or more generally support analyses of hierarchical structure. Here, we address this issue by investigating hierarchical processing in a non-linguistic task. We test the ability to represent recursive hierarchical embedding in the visual domain by contrasting a recursion task with an iteration task. The recursion task requires participants to correctly identify continuations of a hierarchy generating procedure, while the iteration task applies a serial procedure that does not generate new hierarchical levels. In a lesion-based approach, we asked 44 patients with left hemispheric chronic brain lesion to perform recursion and iteration tasks. We modelled accuracies and response times with a drift diffusion model and for each participant obtained parametric estimates for the velocity of information accumulation (drift rates) and for the amount of information accumulated before a decision (boundary separation). We then used these estimates in lesion-behaviour analyses to investigate how brain lesions affect specific aspects of recursive hierarchical embedding. We found that lesions in the posterior temporal cortex decreased drift rate in recursive hierarchical embedding, suggesting an impaired process of rule extraction from recursive structures. Moreover, lesions in inferior temporal gyrus decreased boundary separation. The latter finding does not survive conservative correction but suggests a shift in the decision criterion. As patients also participated in a grammar comprehension experiment, we performed explorative correlation-analyses and found that visual and linguistic recursive hierarchical embedding accuracies are correlated when the latter is instantiated as sentences with two nested embedding levels. While the roles of the inferior temporal gyrus and posterior temporal cortex in linguistic processes are well established, here we show that posterior temporal cortex lesions slow information accumulation (drift rate) in the visual domain. This suggests that posterior temporal cortex is essential to acquire the (knowledge) representations necessary to parse recursive hierarchical embedding in visual structures, a finding mimicking language acquisition in young children. On the contrary, inferior frontal gyrus lesions seem to affect recursive hierarchical embedding processing by interfering with more general cognitive control (boundary separation). This interesting separation of roles, rooted on a domain-general taxonomy, raises the question of whether such cognitive framing is also applicable to other domains.
The human ability to process hierarchical structures has been a longstanding research topic. Howe... more The human ability to process hierarchical structures has been a longstanding research topic. However, the nature of the cognitive machinery underlying this faculty remains controversial. Recursion, the ability to embed structures within structures of the same kind, has been proposed as a key component of our ability to parse and generate complex hierarchies. Here, we investigated the cognitive representation of both recursive and iterative processes in the auditory domain. The experiment used a two-alternative forced-choice paradigm: participants were exposed to three-step processes in which pure-tone sequences were built either through recursive or iterative processes, and had to choose the correct completion. Foils were constructed according to generative processes that did not match the previous steps. Both musicians and non-musicians were able to represent recursion in the auditory domain, although musicians performed better. We also observed that general 'musical' aptitudes played a role in both recursion and iteration, although the influence of musical training was somehow independent from melodic memory. Moreover, unlike iteration, recursion in audition was well correlated with its non-auditory (recursive) analogues in the visual and action sequencing domains. These results suggest that the cognitive machinery involved in establishing recursive representations is domain-general, even though this machinery requires access to information resulting from domain-specific processes.
Self-similarity and recursion as default modes in human cognition
Humans generate recursive hierarchies in a variety of domains, including linguistic, social and v... more Humans generate recursive hierarchies in a variety of domains, including linguistic, social and visuo-spatial modalities. The ability to represent recursive structures has been hypothesized to increase the efficiency of hierarchical processing. Theoretical work together with recent empirical findings suggests that the ability to represent the self-similar structure of hierarchical recursive stimuli may be supported by internal neural representations that compress raw external information and increase efficiency. In order to explicitly test whether the representation of recursive hierarchies depends on internalized rules we compared the processing of visual hierarchies represented either as recursive or non-recursive, using task-free resting-state fMRI data. We aimed to evaluate the relationship between task-evoked functional networks induced by cognitive representations with the corresponding resting-state architecture. We observed increased connectivity within Default Mode Network (DMN) related brain areas during the representation of recursion, while non-recursive representations yielded increased connectivity within the Fronto-Parietal Control-Network. Our results suggest that human hierarchical information processing using recursion is supported by the DMN. In particular, the representation of recursion seems to constitute an internally-biased mode of information-processing that is mediated by both the core and dorsal-medial subsystems of the DMN. Compressed internal rule representations mediated by the DMN may help humans to represent and process hierarchical structures in complex environments by considerably reducing information processing load.
The relationship between linguistic syntax and action planning is of considerable interest in cog... more The relationship between linguistic syntax and action planning is of considerable interest in cognitive science because many researchers suggest that ‘‘motor syntax” shares certain key traits with language. In a recent manuscript in this journal, Vicari and Adenzato (henceforth VA) critiqued Hauser, Chomsky and Fitch’s 2002 (henceforth HCF’s) hypothesis
that recursion is language-specific, and that its usage in other domains is parasitic on language resources. VA’s main argument is that HCF’s hypothesis is falsified by the fact that
recursion typifies the structure of intentional action, and recursion in the domain of action is independent of language. Here, we argue that VA’s argument is incomplete, and that
their formalism can be contrasted with alternative frameworks that are equally consistent with existing data. Therefore their conclusions are premature without further empirical testing and support. In particular, to accept VA’s argument it would be necessary to demonstrate both that humans in fact represent self-embedding in the structure of intentional action, and that language is not used to construct these representations.
We describe a new method to explore recursive cognition in the visual domain. We define recursion... more We describe a new method to explore recursive cognition in the visual domain. We define recursion as the ability to represent multiple hierarchical levels using the same rule, entailing the ability to generate new levels beyond those previously encountered. With this definition recursion can be distinguished from general hierarchical embedding. To investigate this recursion/hierarchy distinction in the visual domain, we developed two novel methods: The Visual Recursion Task (VRT), in which an inferred rule is used to represent new hierarchical levels, and the Embedded Iteration Task (EIT), in which additional elements are added to an existing hierarchical level. We found that adult humans can represent recursion in the visuo-spatial domain, and that this ability is distinct from both general intelligence and the ability to represent iterative processes embedded within hierarchical structures. Compared with embedded iteration, visual recursion correlated positively with other recursive planning tasks (Tower of Hanoi), but not with specific visuo-spatial resources (spatial short-term memory and working memory). We conclude that humans are able to use recursive representations to process complex visuo-spatial hierarchies and that our visual recursion task taps into specific cognitive resources. This method opens exciting opportunities to explore the relationship between visual recursion and language.
Background: The ability to recognize and interpret emotions in others is a crucial
prerequisite o... more Background: The ability to recognize and interpret emotions in others is a crucial
prerequisite of adequate social behavior. Impairments in emotion processing have
been reported from the early stages of Parkinson’s disease (PD). This study aims to
characterize emotion recognition in advanced Parkinson’s disease (APD) candidates for
deep-brain stimulation and to compare emotion recognition abilities in visual and
auditory domains. Method: APD patients, defined as those with levodopa-induced
motor complications (N = 42), and healthy controls (N = 43) matched by gender, age,
and educational level, undertook the Comprehensive Affect Testing System (CATS), a
battery that evaluates recognition of seven basic emotions (happiness, sadness, anger,
fear, surprise, disgust, and neutral) on facial expressions and four emotions on prosody
(happiness, sadness, anger, and fear). APD patients were assessed during the “ON” state.
Group performance was compared with independent-samples t tests. Results:
Compared to controls, APD had significantly lower scores on the discrimination and
naming of emotions in prosody, and visual discrimination of neutral faces, but no
significant differences in visual emotional tasks. Conclusion: The contrasting performance
in emotional processing between visual and auditory stimuli suggests that
APD candidates for surgery have either a selective difficulty in recognizing emotions
in prosody or a general defect in prosody processing. Studies investigating early-stage
PD, and the effect of subcortical lesions in prosody processing, favor the latter interpretation.
Further research is needed to understand these deficits in emotional prosody
recognition and their possible contribution to later behavioral or neuropsychiatric
manifestations of PD.
Vocal learning, prosody, and basal ganglia: Don’t underestimate their complexity
Behavioral and Brain Sciences
Ackermann et al.’s arguments in the target article need sharpening and rethinking at both mechani... more Ackermann et al.’s arguments in the target article need sharpening and rethinking at both mechanistic and evolutionary levels. First, the authors’ evolutionary arguments are inconsistent with recent evidence concerning nonhuman animal rhythmic abilities. Second, prosodic intonation conveys much more complex linguistic information than mere emotional expression. Finally, human adults’ basal ganglia have a considerably wider role in speech modulation than Ackermann et al. surmise.
Cognitive Psychology
The ability to form and use recursive representations while
processing hierarchical structures h... more The ability to form and use recursive representations while
processing hierarchical structures has been hypothesized to rely on language abilities. If so, linguistic resources should inevitably be activated while representing recursion in non-linguistic domains.
In this study we use a dual-task paradigm to assess whether verbal resources are required to perform a visual recursion task. We tested participants across 4 conditions: (1) Visual recursion only, (2) Visual recursion with motor interference (sequential finger tapping), (3) Visual recursion with verbal interference – low load, and (4) Visual recursion with verbal interference – high load. Our results show that the ability to acquire and use visual recursive representations is not affected by the presence of verbal and motor interference tasks. Our finding that visual recursion can be represented
without access to verbal resources suggests that recursion
is available independently of language processing abilities.
Cognition, 2014
The ability to understand and generate hierarchical structures is a crucial component of human co... more The ability to understand and generate hierarchical structures is a crucial component of human cognition, available in language, music, mathematics and problem solving. Recursion is a particularly useful mechanism for generating complex hierarchies by means of self-embedding rules. In the visual domain, fractals are recursive structures in which simple transformation rules generate hierarchies of infinite depth. Research on how children acquire these rules can provide valuable insight into the cognitive requirements and learning constraints of recursion.
Parkinsonism and Related Disorders, 2014
Parkinsonism and Related Disorders, 2014
Deep brain stimulation of the subthalamic nuclei (STN-DBS) for the treatment of levodopa-induced ... more Deep brain stimulation of the subthalamic nuclei (STN-DBS) for the treatment of levodopa-induced motor complications in advanced Parkinson's disease (APD) has been associated with neuropsychiatric disorders. It has been suggested that a postoperative decline in visual emotion recognition is responsible for those adverse events, although there is also evidence that emotional processing deficits can be present before surgery.
NeuroImage, 2014
Hierarchical structures play a central role in many aspects of human cognition, prominently inclu... more Hierarchical structures play a central role in many aspects of human cognition, prominently including both language and music. In this study we addressed hierarchy in the visual domain, using a novel paradigm based on fractal images. Fractals are self-similar patterns generated by repeating the same simple rule at multiple hierarchical levels. Our hypothesis was that the brain uses different resources for processing hierarchies depending on whether it applies a "fractal" or a "non-fractal" cognitive strategy. We analyzed the neural circuits activated by these complex hierarchical patterns in an event-related fMRI study of 40 healthy subjects. Brain activation was compared across three different tasks: a similarity task, and two hierarchical tasks in which subjects were asked to recognize the repetition of a rule operating transformations either within an existing hierarchical level, or generating new hierarchical levels. Similar hierarchical images were generated by both rules and target images were identical. We found that when processing visual hierarchies, engagement in both hierarchical tasks activated the visual dorsal stream (occipito-parietal cortex, intraparietal sulcus and dorsolateral prefrontal cortex). In addition, the level-generating task specifically activated circuits related to the integration of spatial and categorical information, and with the integration of items in contexts (posterior cingulate cortex, retrosplenial cortex, and medial, ventral and anterior regions of temporal cortex). These findings provide interesting new clues about the cognitive mechanisms involved in the generation of new hierarchical levels as required for fractals.
Annals of the New York Academy of Sciences, 2014
Sixty years ago, Karl Lashley suggested that complex action sequences, from simple motor acts to ... more Sixty years ago, Karl Lashley suggested that complex action sequences, from simple motor acts to language and music, are a fundamental but neglected aspect of neural function. Lashley demonstrated the inadequacy of then-standard models of associative chaining, positing a more flexible and generalized "syntax of action" necessary to encompass key aspects of language and music. He suggested that hierarchy in language and music builds upon a more basic sequential action system, and provided several concrete hypotheses about the nature of this system. Here, we review a diverse set of modern data concerning musical, linguistic, and other action processing, finding them largely consistent with an updated neuroanatomical version of Lashley's hypotheses. In particular, the lateral premotor cortex, including Broca's area, plays important roles in hierarchical processing in language, music, and at least some action sequences. Although the precise computational function of the lateral prefrontal regions in action syntax remains debated, Lashley's notion-that this cortical region implements a working-memory buffer or stack scannable by posterior and subcortical brain regions-is consistent with considerable experimental data.
The Past, Present and Future of Language Evolution, 2014
Models are a flourishing and indispensable area of research in language evolution. Here we highli... more Models are a flourishing and indispensable area of research in language evolution. Here we highlight critical issues in using and interpreting models and suggests viable approaches. First, contrasting models can explain the same data and similar modelling techniques can lead to diverging conclusions. This should act as a reminder to use the extreme malleability of modelling parsimoniously when interpreting results. Second, quantitative techniques similar to those used in modelling language evolution have proven themselves inadequate in other disciplines. Cross-disciplinary fertilization is crucial to avoid mistakes previously occurred in other areas. Finally, experimental validation is necessary both to sharpen models' hypotheses, and to support their conclusions. Our belief is that models should be interpreted as quantitative demonstrations of logical possibilities, rather than direct sources of evidence. Only an integration of theoretical principles, quantitative proofs and empirical validation can allow research in the evolution of language to progress.
in Language and Recursion, 2014
Philosophical Transactions of the Royal Society B, 2012
Although recursion has been hypothesized to be a necessary capacity for the evolution of language... more Although recursion has been hypothesized to be a necessary capacity for the evolution of language, the multiplicity of definitions being used has undermined the broader interpretation of empirical results. I propose that only a definition focused on representational abilities allows the prediction of specific behavioural traits that enable us to distinguish recursion from non-recursive iteration and from hierarchical embedding: only subjects able to represent recursion, i.e. to represent different hierarchical dependencies (related by parenthood) with the same set of rules, are able to generalize and produce new levels of embedding beyond those specified a priori (in the algorithm or in the input). The ability to use such representations may be advantageous in several domains: action sequencing, problem-solving, spatial navigation, social navigation and for the emergence of conventionalized communication systems. The ability to represent contiguous hierarchical levels with the same rules may lead subjects to expect unknown levels and constituents to behave similarly, and this prior knowledge may bias learning positively. Finally, a new paradigm to test for recursion is presented. Preliminary results suggest that the ability to represent recursion in the spatial domain recruits both visual and verbal resources. Implications regarding language evolution are discussed.
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Papers by Maurício de Jesus Dias Martins
that recursion is language-specific, and that its usage in other domains is parasitic on language resources. VA’s main argument is that HCF’s hypothesis is falsified by the fact that
recursion typifies the structure of intentional action, and recursion in the domain of action is independent of language. Here, we argue that VA’s argument is incomplete, and that
their formalism can be contrasted with alternative frameworks that are equally consistent with existing data. Therefore their conclusions are premature without further empirical testing and support. In particular, to accept VA’s argument it would be necessary to demonstrate both that humans in fact represent self-embedding in the structure of intentional action, and that language is not used to construct these representations.
prerequisite of adequate social behavior. Impairments in emotion processing have
been reported from the early stages of Parkinson’s disease (PD). This study aims to
characterize emotion recognition in advanced Parkinson’s disease (APD) candidates for
deep-brain stimulation and to compare emotion recognition abilities in visual and
auditory domains. Method: APD patients, defined as those with levodopa-induced
motor complications (N = 42), and healthy controls (N = 43) matched by gender, age,
and educational level, undertook the Comprehensive Affect Testing System (CATS), a
battery that evaluates recognition of seven basic emotions (happiness, sadness, anger,
fear, surprise, disgust, and neutral) on facial expressions and four emotions on prosody
(happiness, sadness, anger, and fear). APD patients were assessed during the “ON” state.
Group performance was compared with independent-samples t tests. Results:
Compared to controls, APD had significantly lower scores on the discrimination and
naming of emotions in prosody, and visual discrimination of neutral faces, but no
significant differences in visual emotional tasks. Conclusion: The contrasting performance
in emotional processing between visual and auditory stimuli suggests that
APD candidates for surgery have either a selective difficulty in recognizing emotions
in prosody or a general defect in prosody processing. Studies investigating early-stage
PD, and the effect of subcortical lesions in prosody processing, favor the latter interpretation.
Further research is needed to understand these deficits in emotional prosody
recognition and their possible contribution to later behavioral or neuropsychiatric
manifestations of PD.
processing hierarchical structures has been hypothesized to rely on language abilities. If so, linguistic resources should inevitably be activated while representing recursion in non-linguistic domains.
In this study we use a dual-task paradigm to assess whether verbal resources are required to perform a visual recursion task. We tested participants across 4 conditions: (1) Visual recursion only, (2) Visual recursion with motor interference (sequential finger tapping), (3) Visual recursion with verbal interference – low load, and (4) Visual recursion with verbal interference – high load. Our results show that the ability to acquire and use visual recursive representations is not affected by the presence of verbal and motor interference tasks. Our finding that visual recursion can be represented
without access to verbal resources suggests that recursion
is available independently of language processing abilities.