Proceedings of the International scientific and practical conference “Science in the Modern World” (January 19-21, 2026) / Publisher website: www.naukainfo.com. - Cambridge, United Kingdom, 2026. - 203 p.

107 Under experimental hypothyroidism, the opposite effect was observed during three training sessions, namely cognitive deficit. The time required to find the escape platform exceeded that of intact controls by 30-54%. At the same time, the duration of the first freezing episodes increased by 3-23 times, indicating excessive anxiety. Emotional load under experimental hypothyroidism transformed the cognitive deficit into enhanced cognitive activity. The latency of defensive responses decreased relative to the “EL” control by 25% (p < 0.05) under chronic emotional load and by 40% (p < 0.05) under acute emotional load. Improvement of spatial memory occurred alongside a significant reduction in excessively pronounced anxiety under experimental hypothyroidism. The duration of the first freezing episodes exceeded the “EL” control by only 47% (p < 0.05) under chronic stress and by 95% (p < 0.05) under acute stress, indicating a state of adaptive physiological anxiety [4, p. 118]. Conclusion. Thus, the level of anxiety determined the process of formation of defensive spatial memory engrams in rats during early ontogenesis under conditions of thyroid gland dysfunction. Excessive anxiety was associated with cognitive deficit (hyperthyroidism + EL and hypothyroidism), whereas rational anxiety improved cognitive activity (hyperthyroidism and hypothyroidism + EL). REFERENCES: 1. Bernal J. Thyroid hormones in brain development and function // Endocrinology . 2015. Vol. 156(6). P. 1970-1980. 2. Zoeller R.T., Rovet J. Timing of thyroid hormone action in the developing brain // Endocrine Reviews . 2004. Vol. 25(1). P. 78-109. 3. Kim J.J., Diamond D.M. The stressed hippocampus, synaptic plasticity and lost memories // Nature Reviews Neuroscience . 2002. Vol. 3. P. 453-462. 4. McEwen B.S. Stress and hippocampal plasticity // Annual Review of Neuroscience . 1999. Vol. 22. P. 105-122.