Noise Correlations Study for Dyslexia

Overseen By Apoorva Bhandari, PhD

Age: 18+

Sex: Any

Travel: May Be Covered

Time Reimbursement: Varies

Trial Phase: Academic

Recruiting

Sponsor: Brown University

Must not be taking: Neuroleptics

Disqualifiers: Claustrophobia, Color blindness, Stroke, others

No Placebo Group

Trial Summary

What is the purpose of this trial?

A fundamental problem in neuroscience is how the brain computes with noisy neurons. An advantage of population codes is that downstream neurons can pool across multiple neurons to reduce the impact of noise. However, this benefit depends on the noise associated with each neuron being independent. Noise correlations refer to the covariance of noise between pairs of neurons, and such correlations can limit the advantages gained from pooling across large neural populations. Indeed, a large body of theoretical work argues that positive noise correlations between similarly tuned neurons reduce the representational capacity of neural populations and are thus detrimental to neural computation. Despite this apparent disadvantage, such noise correlations are observed across many different brain regions, persist even in well-trained subjects, and are dynamically altered in complex tasks. The investigators have advanced the hypothesis that noise correlations may be a neural mechanism for reducing the dimensionality of learning problems. The viability of this hypothesis has been demonstrated in neural network simulations where noise correlations, when embedded in populations with fixed signal-to-noise ratio, enhance the speed and robustness of learning. Here the investigators aim to empirically test this hypothesis, using a combination of computational modeling, fMRI and pupillometry. Establishing a link between noise correlations and learning would open the door to an investigation into how brains navigate a tradeoff between representational capacity and the speed of learning.

Will I have to stop taking my current medications?

The trial excludes participants taking neuroleptic medications, so if you are on these, you would need to stop. For other medications, the protocol does not specify any requirements.

What data supports the effectiveness of the treatment Dynamic perceptual discrimination task for dyslexia?

Research shows that children with dyslexia can improve their brain connectivity and reading skills after receiving targeted instructional treatment, which suggests that specific training tasks can help rewire the brain to better handle reading challenges. ^{1 2 3 4 5}

How does the Dynamic perceptual discrimination task treatment differ from other treatments for dyslexia?

The Dynamic perceptual discrimination task is unique because it focuses on improving the ability to filter out irrelevant noise, which is a specific challenge for individuals with dyslexia. This approach targets the underlying sensory processing deficits, particularly in noise exclusion, rather than just addressing reading skills directly. ^{6 7 8 9 10}

Research Team

Matthew Nassar, PhD

Principal Investigator

Brown University

Eligibility Criteria

This trial is for individuals with dyslexia or tinnitus. Specific eligibility criteria are not provided, but typically participants would need to be in good health and able to perform the tasks required by the study.

Inclusion Criteria

My vision is normal or can be corrected with glasses or contacts.

I am over 18 years old.

Exclusion Criteria

Conditions contraindicated for MRI such as surgical implant that is not MRI compatible, metal fragments in the body, tattoo with metallic ink

Claustrophobia

History of drug abuse and/or alcoholism

Trial Timeline

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Experimental Task

Participants engage in a dynamic perceptual discrimination task involving motion and color information, requiring adaptation to intra-dimensional shifts.

1 week

1 visit (in-person)

Scanning and Analysis

Participants undergo fMRI scanning to measure noise correlations and pupillometry as a proxy for neuromodulatory signaling.

6 months

Follow-up

Participants are monitored for safety and effectiveness after the experimental tasks and scanning sessions.

4 weeks

Treatment Details

Interventions

• Dynamic perceptual discrimination task (Behavioral Intervention)

Trial Overview The study investigates how 'noise correlations' between neurons affect learning. Participants will undergo a dynamic perceptual discrimination task while their brain activity is monitored using fMRI and pupillometry techniques.

Participant Groups

Group I: Dynamic perceptual discrimination task Experimental Treatment 2 Interventions

The task featured two task conditions, each of which required the integration of information from both stimulus dimensions. In each condition, participants viewed a stimulus containing motion and color information and were required to specify one of two possible responses. Within each condition, rules and the response mapping changed occasionally, but always by changing on a fixed feature dimension (ie. rightward/purple, leftward/orange). These uncued intra-dimensional shifts involved translational shifts in the learning boundary, requiring them to adapt their decision making within a familiar dimension. These shifts compelled participants to continuously adjust their learning strategies by focusing on the most relevant feature dimension.

Who Is Running the Clinical Trial?

Brown University

Lead Sponsor

Trials

480

Recruited

724,000+

National Institute of General Medical Sciences (NIGMS)

Collaborator

Trials

315

Recruited

251,000+

Findings from Research

A study involving 39 children (18 with dyslexia and 21 without) showed significant differences in brain connectivity, particularly in the left inferior frontal gyrus, before treatment, indicating distinct neural patterns associated with dyslexia.

After a three-week instructional treatment focused on linguistic skills, children with dyslexia exhibited normalized brain connectivity patterns, aligning with those of their peers without dyslexia, suggesting that targeted educational interventions can effectively alter brain function related to reading.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Abnormal fMRI Connectivity in Children with Dyslexia During a Phoneme Task: Before But Not After Treatment . Richards, TL., Berninger, VW.[2022]

Dyslexic individuals (D-LDs) show comparable performance to normal readers in tasks like speech perception in noise and tone comparison, indicating some preserved auditory processing abilities.

However, D-LDs struggle with forming perceptual anchors and do not benefit from stimulus-specific repetitions, suggesting their core deficit lies in dynamically constructing predictions, which may be linked to specific neuronal circuit mechanisms.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dyslexia and the failure to form a perceptual anchor. Ahissar, M., Lubin, Y., Putter-Katz, H., et al.[2022]

Children with dyslexia showed significant difficulties in localizing sounds and discriminating words, especially in reverberant environments, compared to control children, indicating a potential challenge in classroom settings.

In particular, children with dyslexia had poor performance in word localization at specific angles (0º and +90º) and word discrimination at left angles in no-reverberant conditions, highlighting the impact of sound environment on their auditory processing.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Sound localization and word discrimination in reverberant environment in children with developmental dyslexia. Castro-Camacho, W., Peñaloza-López, Y., Pérez-Ruiz, SJ., et al.[2015]

Adults with dyslexia showed poorer performance in naming speed tasks compared to typically achieving readers, indicating challenges in processing letters and objects, which are linked to reading abilities.

Neuroimaging revealed that dyslexic individuals had increased activation in the left hemisphere reading network and additional brain regions related to memory, suggesting that their brains may work harder to compensate for reading difficulties, while typically achieving readers showed different activation patterns associated with better performance.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Understanding the biological basis of dyslexia at a neural systems level. Al Dahhan, NZ., Kirby, JR., Brien, DC., et al.[2020]

Adults with dyslexia showed improved motion coherence thresholds when the contrast of signal dots was higher than that of noise dots, supporting the noise exclusion hypothesis of dyslexia.

A cue directing attention to low contrast signal dots in high contrast noise helped adults with dyslexia achieve similar motion coherence thresholds as control participants, indicating that attention can mitigate some sensory processing deficits associated with dyslexia.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The influence of contrast on coherent motion processing in dyslexia. Conlon, EG., Lilleskaret, G., Wright, CM., et al.[2022]

Dyslexic children (48 participants) showed significantly higher internal noise estimates in motion discrimination tasks compared to typically developing children, indicating a potential impairment in their ability to process motion accurately.

The study found that perceptual differences in dyslexia extend beyond motion processing to orientation tasks, suggesting that these children may experience broader challenges in visual perception.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Integration of visual motion and orientation signals in dyslexic children: an equivalent noise approach. Manning, C., Hulks, V., Tibber, MS., et al.[2022]

Dyslexics exhibit a specific perceptual deficit in integrating prior information with noisy observations, which is linked to their poor verbal memory and auditory skills, as shown through an auditory discrimination task involving a two-parameter computational model.

The study found that dyslexics underweight their implicit memory of past trials, leading to decreased ability to compensate for perceptual noise, while ERP measurements indicated that their brain responses do not effectively relate current observations to prior experiences.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

A Computational Model of Implicit Memory Captures Dyslexics' Perceptual Deficits. Jaffe-Dax, S., Raviv, O., Jacoby, N., et al.[2022]

Developmental dyslexia (RD) is linked to low-level sensory-processing deficits that affect phonological skills, which are crucial for reading.

Increased neural excitability and noise in brain networks related to reading may contribute to the timing issues that underlie RD, suggesting a potential target for future interventions.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Neural Noise Hypothesis of Developmental Dyslexia. Hancock, R., Pugh, KR., Hoeft, F.[2018]

References

1. England pubmed.ncbi.nlm.nih.gov

Abnormal fMRI Connectivity in Children with Dyslexia During a Phoneme Task: Before But Not After Treatment . [2022]

2. United States pubmed.ncbi.nlm.nih.gov

Dyslexia and the failure to form a perceptual anchor. [2022]

3. Germany pubmed.ncbi.nlm.nih.gov

Sound localization and word discrimination in reverberant environment in children with developmental dyslexia. [2015]

4. England pubmed.ncbi.nlm.nih.gov

Understanding the biological basis of dyslexia at a neural systems level. [2020]

5. United States pubmed.ncbi.nlm.nih.gov

Neural changes following remediation in adult developmental dyslexia. [2022]

6. England pubmed.ncbi.nlm.nih.gov

The influence of contrast on coherent motion processing in dyslexia. [2022]

7. United States pubmed.ncbi.nlm.nih.gov

Deficits in perceptual noise exclusion in developmental dyslexia. [2022]

8. England pubmed.ncbi.nlm.nih.gov

Integration of visual motion and orientation signals in dyslexic children: an equivalent noise approach. [2022]

9. United States pubmed.ncbi.nlm.nih.gov

A Computational Model of Implicit Memory Captures Dyslexics' Perceptual Deficits. [2022]

10. England pubmed.ncbi.nlm.nih.gov

Neural Noise Hypothesis of Developmental Dyslexia. [2018]