Goal-directed Action Planning Research Articles

The value of time in the invigoration of human movements when interacting with a robotic exoskeleton.

Time and effort are thought to be subjectively balanced during the planning of goal-directed actions, thereby setting the vigor of volitional movements. Theoretical models predicted that the value of time should then amount to high levels of effort. However, the time-effort trade-off has so far only been studied for a narrow range of efforts. To investigate the extent to which humans can invest in a time-saving effort, we used a robotic exoskeleton to substantially vary the energetic cost associated with a certain vigor during reaching movements. In this situation, minimizing the time-effort trade-off should lead to high and low human efforts for upward and downward movements, respectively. Consistently, all participants expended substantial amounts of energy upward and remained essentially inactive by harnessing the work of gravity downward, while saving time in both cases. A common time-effort trade-off may therefore determine the vigor of reaching movements for a wide range of efforts.

Stronger brain activation for own baby but similar activation toward babies of own and different ethnicities in parents living in a multicultural environment

Specific facial features in infants automatically elicit attention, affection, and nurturing behaviour of adults, known as the baby schema effect. There is also an innate tendency to categorize people into in-group and out-group members based on salient features such as ethnicity. Societies are becoming increasingly multi-cultural and multi-ethnic, and there are limited investigations into the underlying neural mechanism of the baby schema effect in a multi-ethnic context. Functional magnetic resonance imaging (fMRI) was used to examine parents’ (N = 27) neural responses to (a) non-own ethnic in-group and out-group infants, (b) non-own in-group and own infants, and (c) non-own out-group and own infants. Parents showed similar brain activations, regardless of ethnicity and kinship, in regions associated with attention, reward processing, empathy, memory, goal-directed action planning, and social cognition. The same regions were activated to a higher degree when viewing the parents’ own infant. These findings contribute further understanding to the dynamics of baby schema effect in an increasingly interconnected social world.

Goal-Directed Planning and Goal Understanding by Extended Active Inference: Evaluation through Simulated and Physical Robot Experiments.

We show that goal-directed action planning and generation in a teleological framework can be formulated by extending the active inference framework. The proposed model, which is built on a variational recurrent neural network model, is characterized by three essential features. These are that (1) goals can be specified for both static sensory states, e.g., for goal images to be reached and dynamic processes, e.g., for moving around an object, (2) the model cannot only generate goal-directed action plans, but can also understand goals through sensory observation, and (3) the model generates future action plans for given goals based on the best estimate of the current state, inferred from past sensory observations. The proposed model is evaluated by conducting experiments on a simulated mobile agent as well as on a real humanoid robot performing object manipulation.

Goal-directed action planning in infants with Down syndrome.

Down syndrome (DS) is a neurogenetic disorder associated with risk for executive dysfunction, or difficulties with the cognitive processes required for planning volitional, goal-directed behaviour. This study examines the developmental origins of difficulties with goal-directed action planning in infants with DS to inform our understanding of the cognitive phenotype associated with DS and its implications for intervention. First, the study compared the performance of infants with DS (n=44, mean chronological age=7.5months, SD=2.3) and typically developing infants (n=31, mean chronological age=7.5months, SD=2.9) on plan production and planning efficiency during an early planning task. Next, potential sources of variability in planning behaviour (motor performance and sensory processing) within the DS sample were examined. All infants completed an early planning laboratory task and the Bayley Scales of Infant Development-III Cognitive Scale. The motor and sensory skills of infants with DS were assessed by the motor scales of the Bayley Scales of Infant Development-III and the Infant Sensory Profile-2. DS-related biomedical history information was provided by caregivers for the infants with DS. Between-group differences in planning were observed on the dimensions of strategy production and completion, such that infants with DS were less efficient in their strategy execution than typically developing infants. In the DS group, motor skills and sensory processing were associated with planning efficiency on all components of the early planning task. Less efficient action planning in infants with DS may disrupt the shaping of goal-directed behaviour, and the identification of early risk factors associated with planning efficiency has important implications for early intervention.

Patterns of afferent input to the caudal and rostral areas of the dorsal premotor cortex (6DC and 6DR) in the marmoset monkey.

Corticocortical projections to the caudal and rostral areas of dorsal premotor cortex (6DC and 6DR, also known as F2 and F7) were studied in the marmoset monkey. Both areas received their main thalamic inputs from the ventral anterior and ventral lateral complexes, and received dense projections from the medial premotor cortex. However, there were marked differences in their connections with other cortical areas. While 6DR received consistent inputs from prefrontal cortex, area 6DC received few such connections. Conversely, 6DC, but not 6DR, received major projections from the primary motor and somatosensory areas. Projections from the anterior cingulate cortex preferentially targeted 6DC, while the posterior cingulate and adjacent medial wall areas preferentially targeted 6DR. Projections from the medial parietal area PE to 6DC were particularly dense, while intraparietal areas (especially the putative homolog of LIP) were more strongly labeled after 6DR injections. Finally, 6DC and 6DR were distinct in terms of inputs from the ventral parietal cortex: projections to 6DR originated preferentially from caudal areas (PG and OPt), while 6DC received input primarily from rostral areas (PF and PFG). Differences in connections suggest that area 6DR includes rostral and caudal subdivisions, with the former also involved in oculomotor control. These results suggest that area 6DC is more directly involved in the preparation and execution of motor acts, while area 6DR integrates sensory and internally driven inputs for the planning of goal-directed actions. They also provide strong evidence of a homologous organization of the dorsal premotor cortex in New and Old World monkeys.

P 60. Using TMS to investigate the role of EBA during action planning

The extrastriate body area (EBA) has initially been defined as a visual ventral-stream area involved in perception of human body parts ( Downing et al., 2001 ). However, subsequent studies observed non-specific activation of EBA during motor tasks ( Astafiev et al., 2004 ; Kuhn et al., 2009). Dijkerman et al. (2009) showed that damage to the ventral stream, likely including EBA, modulates behaviour such that patients can still grasp objects, but they do so without anticipation of future (body) states. Interestingly, clinical research suggested that EBA is engaged by patients suffering from Parkinson’s disease to compensate for impairments of the premotor cortices ( Helmich et al., 2007 , van Nuenen et al., 2012 ). Recently, based on neurophysiological studies in healthy subjects, we proposed how EBA might contribute to motor control, namely by representing desired goal-postures during planning of goal-directed actions ( Zimmermann et al., 2013 ). In detail, our results showed that EBA provides a visual representation of a desired goal-state that is subsequently used by frontal and posterior parietal motor structures when planning an action. Among the latter structures the intraparietal sulcus (IPS) has been ascribed a key-role in simulating action plans and monitor their execution ( De Lange et al., 2005 ). Here we use transcranial magnetic stimulation (TMS) to test whether EBA represents an action’s goal-state. We expect that stimulating EBA early during the planning phase of an action will interfere with the action plan, just like late stimulation of the parietal cortex. On the other hand, stimulating EBA late during planning, as well as stimulating IPS early, should not cause interference. Participants grasp a bar and rotate it into an instructed orientation. Vision of the bar and their own hand is blocked from the moment they start moving. During the planning phase single pulse TMS is applied randomly to either left IPS or left EBA; sham TMS is used as an additional control condition. Pulses are delivered early (100–300 ms after trial onset) or late (300–500 ms after trial onset) during the planning phase (average planning times are between 500 and 600 ms). We measure reaction times and movement errors (measured as discrepancy between instructed and realized final bar orientation), as well as kinematics of the participant’s right hand. Preliminary results ( N = 6) suggest that there is an interaction between timing of the TMS pulse and the stimulated brain region ( F (1,20) = 3.26, p = .086; Fig. 1). Participants tend to make larger errors when TMS is applied to EBA early during the planning phase, compared to IPS early as well as EBA late. The reverse seems the case for stimulation of IPS: late stimulation increases errors relative to early IPS stimulation and late EBA stimulation. Reaction times are modulated by the timing of the TMS pulse, but are not influenced by the site of stimulation, and do not differ from sham TMS. Our preliminary results suggest that EBA does play a role in planning of goal-directed actions. The interaction between TMS timing and TMS site indicates that the different brain regions, EBA and IPS, are involved in sequential order, starting with EBA and followed by the parietal structures.

Motor Planning Is Facilitated by Adopting an Action's Goal Posture: An fMRI Study

Motor planning is a hierarchical process that is typically organized around an action's goal (e.g., drinking from a cup). However, the motor plan depends not only on the goal but also on the current body state. Here, we investigated how one's own body posture interacts with planning of goal-directed actions. Participants engaged in a grasp selection (GS) task while we manipulated their arm posture. They had to indicate how they would grasp a bar when transporting it from a start to goal position and orientation. We compared situations in which one's body posture was in-congruent with the start posture and/or goal posture of the planned movement. Behavioral results show that GS took longer when one's own body state was incongruent with the goal posture of the planned movement. Correspondingly, neural activity in the intraparietal sulcus (IPS) and extrastriate body area (EBA) was modulated by congruency between the body state and the action plan. IPS was sensitive to overall congruency between body posture and action plan, while the EBA was sensitive specifically to goal posture congruency. Together, our results suggest that IPS maintains an internal state of one's own body posture, while EBA contains a representation of the goal posture of the action plan.

Tonically active neurons in the primate caudate nucleus and putamen differentially encode instructed motivational outcomes of action.

To achieve a goal, animals procure immediately available rewards, escape from aversive events, or endure the absence of rewards. The neuronal substrates for these goal-directed actions include the limbic system and the basal ganglia. In the striatum, tonically active neurons (TANs), presumed cholinergic interneurons, were originally shown to respond to reward-associated stimuli and to evolve their activity through learning. Subsequent studies revealed that they also respond to aversive event-associated stimuli such as an airpuff on the face and that they are less selective to whether the stimuli instruct reward or no reward. To address this paradox, we designed a set of experiments in which macaque monkeys performed a set of visual reaction time tasks while expecting a reward, during escape from an aversive event, and in the absence of a reward. We found that TANs respond to instruction stimuli associated with motivational outcomes (312 of 390; 80%) but not to unassociated ones (51 of 390; 13%), and that they mostly differentiate associated instructions (217 of 312; 70%). We also found that a higher percentage of TANs in the caudate nucleus respond to stimuli associated with motivational outcomes (118 of 128; 92%) than in the putamen (194 of 262; 74%), whereas a higher percentage of TANs in the putamen respond to go signals for the lever release (112 of 262; 43%) than in the caudate nucleus (27 of 128; 21%), especially for an action expecting a reward. These findings suggest a distinct, pivotal role of TANs in the caudate nucleus and putamen in encoding instructed motivational contexts for goal-directed action planning and learning.