Block Building Task Identifies Distinct Groups of Left/Right-hand Choice Patterns After Unilateral Peripheral Nerve Injury

Our laboratory focuses on studying handedness. We investigate the brain mechanisms that determine whether you're more skilled with or more inclined to use your right or left hand. We also explore how these mechanisms can be rewired to help individuals who lose the ability to use their dominant hand.

Most studies assess handedness with questionnaires, but self-reports can be biased or inaccurate, and it's been established that these questionnaires don't really capture how often people use their left versus right hands in real life. We need to measure actual hand usage, not what people think about their hand usage. A few other techniques exist to measure left versus right hand usage, but none of them are both quantitative and functional.

For clinically relevant results, we need to know how much you use each hand when you pick up an object and actually use that object to achieve a goal you care about. Our findings reveal that some patients avoid using their injured hand, while others continue or even increase their reliance on it. Now that we know this, we can investigate the reasons behind these differences.

What factors determine which group an individual falls into, and which approach will best support the recovery or compensation that person needs? To begin, build four block building task models using one of the 10 standard bricks for each model. Ensure that, upon completion, 40 more bricks, plus spares, remain.

Glue each model together to secure the bricks in place. Label each model with a number on the back side. Next, cut out a five-inch square baseplate notch from the poster board at the center of one long side.

Place the bricks on the poster board. On the poster board, outline each brick's location using a pen or pencil, leaving a two-millimeter border around each brick. Place a label outside each brick outline to indicate the brick type, positioning it for readability by an experimenter seated opposite the baseplate.

For any asymmetrical bricks, add an arrow to the label to indicate a consistent orientation for the brick. Cut out the rectangular outlines from the poster board to create labeled spaces for each of the 40 bricks. Set up the block building task equipment before the participant arrives in the room.

Align the poster board on the table, with its notch at one edge of the table where the participant will sit. Then, place the baseplate in the poster board's notch and tape it securely along two sides. Now, arrange a chair without wheels in front of the baseplate.

Place the appropriate brick into each cutout on the poster board. Then, remove the poster board so only the bricks and baseplate remain. Determine the order of the four models using either counterbalancing or randomization.

Place the stand and model on the experimenter's side of the table. Next, position the camera 30 to 50 centimeters above the table, opposite the baseplate. Ensure that the camera has a clear view of the workspace that includes the blocks, hands, and model numbers.

Ensure that the model does not block or obscure the bricks. Then, remove the model. Ensure the capacity to perform offline tallying from the video is available.

Or alternatively, have three experimenters ready to tally left and right reaches during the main task execution. Next, admit the participant to the room. Ask the participant to sit in the chair, ensuring that the bricks are clearly visible on the table.

Remove or cover any visible identifiers on the participant to prevent capturing personally identifiable information. Check the participant for any identifiers, including the participant's face, badges, and tattoos. Adjust the camera to capture the bricks clearly and the area where the participant will build the shapes, including space above the model, ensuring the participant's face remains out of the frame.

Direct the participant to use the shapes on the table to construct the model on the green baseplate, ensuring the colors match exactly. Then, instruct the participant to pick up each piece instead of dragging it across the table. Instruct them to avoid setting pieces aside for later.

Only pick them up when ready to use them. Address any questions from the participant by repeating or clarifying the script without introducing new information. To start data collection, ask the participant to place their hands next to the baseplate.

Inform the participant that the recording is about to begin, and then start the recording. Place the first model on the stand with the number label facing the experimenter. Then, say go, and wait for the participant to complete their model.

After the participant completes the model, remove both the experimenter's glued model and the participant's assembled model from the table. The block building task data showed healthy right-handed adults primarily used their dominant hand, at a rate of approximately 0.63. Patients with unilateral peripheral nerve injuries to the dominant hand exhibited an average rate of dominant hand usage comparable to that of healthy adults.

However, individual patients showed variations, with some favoring excessive use of either the injured or uninjured hand. Cluster analysis identified three distinct groups based on hand usage fractions, never using the dominant hand, typical usage, and constant usage. 57%of patients displayed atypical hand usage, with clustering independent of whether the dominant hand or non-dominant hand was injured.

Clinical factors, such as nerve affected, injury location, and pain did not predict hand usage patterns in right-handed patients.