Substituted pyrazolopyrimidine derivatives of formula (I) wherein Y.sup.1, Y.sup.2, Y.sup.3, Y.sup.4 represent N or C--, whereby at least two of the groups Y.sup.1 to Y.sup.4 represent a carbon atom, R.sup.1 represents chloro or bromo, R.sup.2 to R.sup.7 represent e.g. hydrogen, methyl or ethyl; and R.sup.10 and R.sup.11 independently represent e.g. hydrogen or C.sub.1-C.sub.6alkyl, are potent mGluR5 modulators and are useful for the prevention of acute and chronic neurological disorders.