Male flies expressing HDAC4^{Scer\UAS.hs.T:Zzzz\FLAG} in adulthood (under the control of Scer\GAL4^ey-OK107 and Scer\GAL80^ts.αTub84B) display the full repertoire of normal courtship behaviours and there is no difference between these flies and wild-type flies in naive courtship activity. Control males retain normal long-term memory, while HDAC4^{Scer\UAS.hs.T:Zzzz\FLAG}-overexpression mutants display a significant impairment. Short-term memory isn't affected. Expression of HDAC4^{Scer\UAS.hs.T:Zzzz\FLAG} under the control of Scer\GAL4^Mef2.247 during adulthood impairs long-term memory but does not affect short-term memory.

Overexpression of HDAC4^{Scer\UAS.hs.T:Zzzz\FLAG} in α/β and α'/β' Kenyon cell subtypes during adulthood, under the control of Scer\GAL4^c739 and Scer\GAL4^c305a respectively (and Scer\GAL80^ts.αTub84B) does not have a significant effect on long-term memory. However, expression of HDAC4^{Scer\UAS.hs.T:Zzzz\FLAG} in γ neurons, under the control of Scer\GAL4¹⁴⁷¹ and Scer\GAL80^ts.αTub84B recapitulates the impairment on long-term memory seen upon expression under the control of Scer\GAL4^ey-OK107 or Scer\GAL4^Mef2.247 (and Scer\GAL80^ts.αTub84B).