Table 1.

Summary of studies examining LTP phenotypes in littermate and non-littermate Fmr1 KO mice. (Studies examining LTP in Fmr1 KO mice were subdivided into three groups: (i) littermate, (ii) non-littermate mice, and (iii) undefined (breeding scheme could not be determined). Only the Fmr1 KO and Fmr1 KO2 (missing Fmr1 mRNA) mouse models of FXS are included. The LTP genotype and brain area studied are shown. Abbreviations: mPFC, medial pre-frontal cortex; LA, lateral amygdala; DG, dentate gyrus; ACC, anterior cingulate cortex; LPP, lateral perforant pathway; MPP, medial perforant pathway; TA, temporoammonic; aud cortex, auditory cortex; MF, mossy fibre; PP, pairing protocol; β-AR, β-adrenoceptors; HFS, high-frequency stimulation; TBS, theta-burst stimulation; mGluR, metabotropic glutamate receptor; STDP, spike timing-dependent plasticity; TBSP, TBS pairing protocol; NOR, novel object recognition; C/A, commissural/associational; LFS, low-frequency stimulation.)

	LTP phenotype	studies	ref.	brain area	induction protocol; notes
littermate	increase	Pilpel et al. 2009a ,b	[55]	CA1	PP (age- and protocol- dependent effects); Fmr1 KO2
		Connor et al. 2011a	[58]	CA1	β-AR-dependent heterosynaptic plasticity
		Martin et al. 2023	[51]	Cerebellum	100 stimuli, 10 Hz; presynaptic LTP mediated by β-AR (low [Ca])
	no change	Godfraind et al. 1996	[53]	CA1	HFS
		Paradee et al. 1999	[54]	CA1	TBS
		Li et al. 2002c	[12]	CA1	TBS (brain area-dependent effect)
		Pilpel et al. 2009	[55]	CA1	PP (age-dependent) / TBS (protocol-dependent); Fmr1 KO2
		Zhang et al. 2009a , b	[56]	CA1	HFS / Fmr1 KO; littermate: Fmr1+/− mother and Fxr2−/y father
		Auerbach & Bear 2010	[57]	CA1	HFS
		Connor et al. 2011a	[58]	CA1	HFS-induced synaptic tagging and capture
		Franklin et al. 2014ac	[29]	CA1	HFS (hippocampal region-dependent effect)
		Bostrom et al. 2015c	[32]	CA1	HFS (hippocampal region-dependent effect)
		Ghilan et al. 2015c	[33]	CA1	HFS (hippocampal region-dependent effect)
		Martin et al. 2016c	[36]	mPFC	TBS (area dependent); Fmr1 KO2
	reduction	Li et al. 2002c	[12]	cortex	TBS (brain area-dependent effect)
		Suvrathan et al. 2010	[20]	LA	HFS; mGluR-dependent LTP
		Eadie et al. 2012	[23]	DG	HFS
		Padmashri et al. 2013	[26]	cortex	chemical LTP
		Boda et al. 2014	[27]	CA1	TBS
		Franklin et al. 2014ac	[29]	DG	HFS (hippocampal region-dependent effect)
		Franklin et al. 2014b	[30]	DG	HFS
		Bostrom et al. 2015c	[32]	DG	HFS (hippocampal region-dependent effect)
		Ghilan et al. 2015c	[33]	DG	HFS (hippocampal region-dependent effect)
		Neuhofer et al. 2015	[35]	accumbens	STDP
		Martin et al. 2016b	[36]	mPFC	TBS (age-dependent effect); Fmr1 KO2
		Yau et al. 2016	[37]	DG	HFS; Female Fmr1 HET mice
		Feuge et al.2019	[41]	CA1	chemical LTP; no increase in mEPSC amplitude
		Hwang et al. 2022	[46]	CA1	PP; interneurons
		Martin et al. 2023a	[51]	cerebellum	100 stimuli, 10 Hz; presynaptic LTP mediated by β-AR (high [Ca])
non-littermate	increase	Brager et al. 2012	[60]	CA1	TBSP
		Routh et al. 2013	[61]	CA1	TBSP
		Borreca et al. 2023a	[49]	DG	HFS; 24 hour post NOR / protocol-dependent
	no change	Lauterborn et al. 2007a	[15]	CA1	TBS (protocol-dependent effect)
		Seese et al. 2012	[59]	CA1	TBS; reported 5 min post-induction
		Lundbye et al. 2018b	[38]	CA1	TBS (protocol-dependent effect)
		Wang et al. 2018a	[40]	DG	Optogenetic induction protocol; C / A pathway
		Banke & Barria 2020b	[42]	CA1	LFS; 3 Hz, 2 min (age dependent)
		Borreca et al. 2023a	[49]	DG	HFS; No NOR (protocol-dependent effect)
	reduction	Lauterborn et al. 2007a	[16]	CA1	TBS (protocol-dependent effect)
		Meredith et al. 2007	[17]	PFC	STDP; increased threshold
		Wilson & Cox 2007	[18]	Neocortex	HFS
		Lee et al. 2011	[21]	CA1	TBS
		Xu et al. 2012a	[24]	ACC	PP
		Xu et al. 2012b	[25]	ACC	PP
		Lundbye et al. 2018b	[38]	CA1	TBS (protocol-dependent effect)
		Martinez & Tejada-Simon 2018	[39]	CA1	TBS
		Wang et al. 2018a	[40]	DG	HFS/ pairing protocol; both MPP and LPP
		Banke & Barria 2020b	[42]	CA1	LFS; 3 Hz, 2 min (age-dependent effect)
		Ostrovskaya et al. 2020	[52]	CA1	TBS; Lower probability of late-LTP in P21 KOs (studied < 2 to 5 week)
		Seese et al. 2020	[43]	CA1	TBS
		Zhan et al. 2020	[44]	Cerebellum	TBS
		Ordemann et al. 2021	[45]	CA1 (TA)	TBS
		Jeon et al. 2022	[47]	CA1	TBS
		Borreca et al. 2023a	[49]	DG	HFS; 1 hour post NOR (protocol-dependent effect)
		Li et al. 2023	[50]	mPFC	TBS
undefined	no change	Larson et al. 2005b	[13]	APC / CA1	TBS (age-dependent lack of effect; APC)
	reduction	Larson et al. 2005b	[13]	APC	TBS (age-dependent effect)
		Zhao et al. 2005	[14]	ACC/LA	PP
		Hu et al. 2008	[18]	CA1	PP; acute and cultured slices
		Shang et al. 2009	[19]	CA1	Chemical LTP
		Yun & Trommer 2011	[22]	DG	TBS
		Chen et al. 2014	[28]	ACC	TBS
		Yang et al. 2014	[31]	Aud cortex	HFS; mGluR dependent LTP
		Koga et al. 2015	[34]	ACC	LFS; 2 Hz, 2 min; Presynaptic LTP
		Monday et al. 2022	[48]	DG	25 Hz, 3X + d-APV; conditional KO of FMRP in Granule Cells

^a Diverging results within paper due to induction protocol difference.

^b Diverging results within paper due to age differences.

^c Diverging results within paper due to brain area differences.