MRI volume changes during methamphetamine rehabilitation were associated with usual treatment and additional working-memory training. The scans did not establish growth of new neurons or prove that a larger region necessarily represented better function.
Brooks and colleagues recruited 66 men: 41 methamphetamine patients and 25 healthy controls. Within the patient cohort, 17 received treatment as usual and 24 received usual treatment plus daily 30-minute working-memory training over four weeks. MRI was analyzed using voxel-based morphometry, a method for comparing regional tissue-volume estimates. This was a human treatment study, not an animal histology experiment.
Usual treatment was associated with larger striatal volumes at follow-up. The training condition showed more widespread increases involving basal-ganglia regions and nearby structures, alongside cerebellar volume changes. The study also examined working-memory performance and self-reported impulsivity. Different analyses addressed group, time and performance; their results should not be collapsed into a single claim that training enlarged every relevant region.
MRI morphometry cannot distinguish all possible cellular and physiological contributors to an observed volume change. It does not directly count neurons, synapses or dopamine receptors. A larger volume is also not inherently a favorable outcome: interpretation depends on the region, comparison, time course and relationship with measured function. A biological explanation such as neuroplasticity remains an interpretation rather than a direct tissue observation.
All patients were undergoing inpatient treatment and abstinence. Nutrition, recovery-related changes and other components of care may contribute to longitudinal differences. The authors discussed malnourishment and refeeding as possible influences on brain-volume findings. The selected, all-male sample and short follow-up further limit generalization. A training-associated imaging pattern does not by itself establish durable cognitive recovery, reduced methamphetamine use or impairment at an earlier event. The strongest use of this evidence is to motivate studies that connect replicated structural change with specific, lasting functional outcomes.
See also longer-term cognitive change during methamphetamine abstinence.