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Aging into Perceptual Control: A Dynamic Causal Modeling for fMRI Study of Bistable Perception.

Dowlati E, Adams SE, Stiles AB, Moran RJ - Front Hum Neurosci (2016)

Bottom Line: Our aim was to understand the effective connectivity associated with volitional control of ambiguous visual stimuli and to test whether greater top-down control of early visual networks emerged with advancing age.In contrast, our younger cohort did not exhibit any consistent connectivity effects but instead showed a loss of driving inputs to orbitofrontal sources following training.These findings suggest that perceptual beliefs are more readily controlled by top-down strategies in older adults and introduce age-dependent neural mechanisms that may be important for understanding aberrant belief states associated with psychopathology.

View Article: PubMed Central - PubMed

Affiliation: Virginia Tech Carilion School of Medicine Roanoke, VA, USA.

ABSTRACT
Aging is accompanied by stereotyped changes in functional brain activations, for example a cortical shift in activity patterns from posterior to anterior regions is one hallmark revealed by functional magnetic resonance imaging (fMRI) of aging cognition. Whether these neuronal effects of aging could potentially contribute to an amelioration of or resistance to the cognitive symptoms associated with psychopathology remains to be explored. We used a visual illusion paradigm to address whether aging affects the cortical control of perceptual beliefs and biases. Our aim was to understand the effective connectivity associated with volitional control of ambiguous visual stimuli and to test whether greater top-down control of early visual networks emerged with advancing age. Using a bias training paradigm for ambiguous images we found that older participants (n = 16) resisted experimenter-induced visual bias compared to a younger cohort (n = 14) and that this resistance was associated with greater activity in prefrontal and temporal cortices. By applying Dynamic Causal Models for fMRI we uncovered a selective recruitment of top-down connections from the middle temporal to Lingual gyrus (LIN) by the older cohort during the perceptual switch decision following bias training. In contrast, our younger cohort did not exhibit any consistent connectivity effects but instead showed a loss of driving inputs to orbitofrontal sources following training. These findings suggest that perceptual beliefs are more readily controlled by top-down strategies in older adults and introduce age-dependent neural mechanisms that may be important for understanding aberrant belief states associated with psychopathology.

No MeSH data available.


Related in: MedlinePlus

Experimental design and age effects on trained stimulus. (A) Block 1: the ambiguous Rubin vase was shown for 60 s, where participants indicated their perception, faces or vase, with a button press. This was repeated 6 times and each trial was separated by a 6 s fixation cross. Block 2: a non-ambiguous, modified Rubin vase was shown for 16 s, where participants indicated when the fixation-cross appeared on either the left or right of the image. This was repeated 16 times and each trial was separated by a 4 s fixation cross. Block 3 was identical in design to Block 1. (B) Left: the average duration in viewing faces (the biased percept) in Block 3 compared to Block 1 for the young cohort (light red) and older cohort (dark red). Right: the ratio of these durations—i.e., the perceptual biasing effect, was significantly different between the younger and older groups *p < 0.05.
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Figure 1: Experimental design and age effects on trained stimulus. (A) Block 1: the ambiguous Rubin vase was shown for 60 s, where participants indicated their perception, faces or vase, with a button press. This was repeated 6 times and each trial was separated by a 6 s fixation cross. Block 2: a non-ambiguous, modified Rubin vase was shown for 16 s, where participants indicated when the fixation-cross appeared on either the left or right of the image. This was repeated 16 times and each trial was separated by a 4 s fixation cross. Block 3 was identical in design to Block 1. (B) Left: the average duration in viewing faces (the biased percept) in Block 3 compared to Block 1 for the young cohort (light red) and older cohort (dark red). Right: the ratio of these durations—i.e., the perceptual biasing effect, was significantly different between the younger and older groups *p < 0.05.

Mentions: Each participant received task instructions and completed an instruction quiz prior to the scanning session. The fMRI task consisted of three blocks: ambiguous Block 1, “Biasing” Non-ambiguous Block 2, and ambiguous Block 3 (Figure 1A). In ambiguous Block 1, the Rubin vase was presented for 60 s, followed by a fixation cross displayed for 6 s (Rubin, 1921). Participants were instructed to indicate via button press whether they perceived two faces or a vase initially as well as every time their perception switched over the 60-s trial. This experimental design was similar to that employed in Sterzer et al. (2009) in that participants were not given instructions to focus on one perception over the other. All button presses were recorded and this was repeated for a total of six trials. Participants were then shown a modified, non-ambiguous stimulus during the “Biasing” Non-ambiguous Block 2. This non-ambiguous stimulus was intended to explicitly portray two faces by modifying it in a way that the two faces was the most likely perception gained from looking at the stimulus. By presenting such an image, we intended to “train” or “bias” participants toward the perception of the faces vs. a vase when they viewed the ambiguous figure. The non-ambiguous stimulus was presented for a total of 16 s, followed by a fixation cross displayed for 4 s. This was repeated for a total of 16 trials. When the non-ambiguous stimuli were presented, a fixation cross would appear at random to either the left or right of the screen and participants were instructed to indicate via button press when the fixation cross appeared. In Ambiguous Block 3, participants were again presented the ambiguous Rubin vase image for 60 s, followed by a fixation cross displayed for 6 s and instructed to indicate via button press their initial perception and their subsequent perceptual switches. This repeated for a total of six trials. To summarize: in two blocks (Blocks 1 and 3), we showed participants a non-modified ambiguous Rubin vase figure. The non-ambiguous block (block 2) was the “training” block in which the participant was shown a modified version of the Rubin vase diagram eliciting a stable perception showing two faces, where the top and bottom borders were removed. This was a similar modification to the image as presented in Wang et al. (2013). The non-ambiguous image was also chosen as a result of pilot data (not reported) which suggested the Rubin image modified to elicit a face-bias was a stronger non-ambiguous image than the Rubin image modified to elicit a vase-bias.


Aging into Perceptual Control: A Dynamic Causal Modeling for fMRI Study of Bistable Perception.

Dowlati E, Adams SE, Stiles AB, Moran RJ - Front Hum Neurosci (2016)

Experimental design and age effects on trained stimulus. (A) Block 1: the ambiguous Rubin vase was shown for 60 s, where participants indicated their perception, faces or vase, with a button press. This was repeated 6 times and each trial was separated by a 6 s fixation cross. Block 2: a non-ambiguous, modified Rubin vase was shown for 16 s, where participants indicated when the fixation-cross appeared on either the left or right of the image. This was repeated 16 times and each trial was separated by a 4 s fixation cross. Block 3 was identical in design to Block 1. (B) Left: the average duration in viewing faces (the biased percept) in Block 3 compared to Block 1 for the young cohort (light red) and older cohort (dark red). Right: the ratio of these durations—i.e., the perceptual biasing effect, was significantly different between the younger and older groups *p < 0.05.
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Related In: Results  -  Collection

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Figure 1: Experimental design and age effects on trained stimulus. (A) Block 1: the ambiguous Rubin vase was shown for 60 s, where participants indicated their perception, faces or vase, with a button press. This was repeated 6 times and each trial was separated by a 6 s fixation cross. Block 2: a non-ambiguous, modified Rubin vase was shown for 16 s, where participants indicated when the fixation-cross appeared on either the left or right of the image. This was repeated 16 times and each trial was separated by a 4 s fixation cross. Block 3 was identical in design to Block 1. (B) Left: the average duration in viewing faces (the biased percept) in Block 3 compared to Block 1 for the young cohort (light red) and older cohort (dark red). Right: the ratio of these durations—i.e., the perceptual biasing effect, was significantly different between the younger and older groups *p < 0.05.
Mentions: Each participant received task instructions and completed an instruction quiz prior to the scanning session. The fMRI task consisted of three blocks: ambiguous Block 1, “Biasing” Non-ambiguous Block 2, and ambiguous Block 3 (Figure 1A). In ambiguous Block 1, the Rubin vase was presented for 60 s, followed by a fixation cross displayed for 6 s (Rubin, 1921). Participants were instructed to indicate via button press whether they perceived two faces or a vase initially as well as every time their perception switched over the 60-s trial. This experimental design was similar to that employed in Sterzer et al. (2009) in that participants were not given instructions to focus on one perception over the other. All button presses were recorded and this was repeated for a total of six trials. Participants were then shown a modified, non-ambiguous stimulus during the “Biasing” Non-ambiguous Block 2. This non-ambiguous stimulus was intended to explicitly portray two faces by modifying it in a way that the two faces was the most likely perception gained from looking at the stimulus. By presenting such an image, we intended to “train” or “bias” participants toward the perception of the faces vs. a vase when they viewed the ambiguous figure. The non-ambiguous stimulus was presented for a total of 16 s, followed by a fixation cross displayed for 4 s. This was repeated for a total of 16 trials. When the non-ambiguous stimuli were presented, a fixation cross would appear at random to either the left or right of the screen and participants were instructed to indicate via button press when the fixation cross appeared. In Ambiguous Block 3, participants were again presented the ambiguous Rubin vase image for 60 s, followed by a fixation cross displayed for 6 s and instructed to indicate via button press their initial perception and their subsequent perceptual switches. This repeated for a total of six trials. To summarize: in two blocks (Blocks 1 and 3), we showed participants a non-modified ambiguous Rubin vase figure. The non-ambiguous block (block 2) was the “training” block in which the participant was shown a modified version of the Rubin vase diagram eliciting a stable perception showing two faces, where the top and bottom borders were removed. This was a similar modification to the image as presented in Wang et al. (2013). The non-ambiguous image was also chosen as a result of pilot data (not reported) which suggested the Rubin image modified to elicit a face-bias was a stronger non-ambiguous image than the Rubin image modified to elicit a vase-bias.

Bottom Line: Our aim was to understand the effective connectivity associated with volitional control of ambiguous visual stimuli and to test whether greater top-down control of early visual networks emerged with advancing age.In contrast, our younger cohort did not exhibit any consistent connectivity effects but instead showed a loss of driving inputs to orbitofrontal sources following training.These findings suggest that perceptual beliefs are more readily controlled by top-down strategies in older adults and introduce age-dependent neural mechanisms that may be important for understanding aberrant belief states associated with psychopathology.

View Article: PubMed Central - PubMed

Affiliation: Virginia Tech Carilion School of Medicine Roanoke, VA, USA.

ABSTRACT
Aging is accompanied by stereotyped changes in functional brain activations, for example a cortical shift in activity patterns from posterior to anterior regions is one hallmark revealed by functional magnetic resonance imaging (fMRI) of aging cognition. Whether these neuronal effects of aging could potentially contribute to an amelioration of or resistance to the cognitive symptoms associated with psychopathology remains to be explored. We used a visual illusion paradigm to address whether aging affects the cortical control of perceptual beliefs and biases. Our aim was to understand the effective connectivity associated with volitional control of ambiguous visual stimuli and to test whether greater top-down control of early visual networks emerged with advancing age. Using a bias training paradigm for ambiguous images we found that older participants (n = 16) resisted experimenter-induced visual bias compared to a younger cohort (n = 14) and that this resistance was associated with greater activity in prefrontal and temporal cortices. By applying Dynamic Causal Models for fMRI we uncovered a selective recruitment of top-down connections from the middle temporal to Lingual gyrus (LIN) by the older cohort during the perceptual switch decision following bias training. In contrast, our younger cohort did not exhibit any consistent connectivity effects but instead showed a loss of driving inputs to orbitofrontal sources following training. These findings suggest that perceptual beliefs are more readily controlled by top-down strategies in older adults and introduce age-dependent neural mechanisms that may be important for understanding aberrant belief states associated with psychopathology.

No MeSH data available.


Related in: MedlinePlus