Plasma and serum BDNF differentially relate to fNIRS prefrontal cortex activity during executive function and memory...

Brain-Derived Neurotrophic Factor (BDNF) is known to play significant roles in memory through synaptic plasticity and hippocampal volume. However, its function in the prefrontal cortex remains less explored, and differences in the associations of plasma BDNF (pBDNF) and serum BDNF (sBDNF) with cortical function are at present poorly understood. Therefore, this study aimed to investigate whether there are differential relationships between pBDNF and sBDNF with prefrontal cortex activity during executive function and episodic memory tasks.

Twenty-three participants (7 females, age 32 ± 15 years) provided venous blood samples and completed executive function and episodic memory tasks at three time points (weeks 0, 6, and 12). Prefrontal cortex function was additionally measured using functional near-infrared spectroscopy (fNIRS) in week 6.

There was a significant positive association between pBDNF (but not sBDNF) and episodic memory performance (p < 0.05), and with higher CBSI-beta in the left orbitofrontal and frontopolar regions (R range = 0.41 to 0.58; p range = 0.004 to 0.049) during both encoding and retrieval blocks. During inhibition and attention tasks, pBDNF correlated with lower CBSI-beta in the medial frontopolar and orbitofrontal regions (R range = -0.41 to -0.55; p range = 0.007 to 0.05) but did not predict cognitive performance. In contrast, sBDNF was associated with higher CBSI-beta across the prefrontal cortex during endogenous attending only, but was not associated with performance on any task.

Better cognitive performance and higher neural activity during episodic memory suggest that pBDNF may be involved in supporting prefrontal cortex functions for episodic memory. Different associations between pBDNF and sBDNF and both cognitive and imaging outcomes may reflect the differing bioavailability of these two BDNF pools, with implications for future mechanistic studies.