diff --git a/src/forward.jl b/src/forward.jl
index 4790036..e11e36c 100644
--- a/src/forward.jl
+++ b/src/forward.jl
@@ -40,48 +40,53 @@ function (kfn::kfn_1)(input::AbstractArray)
                 reshape(kfn.alif_zt, (size(input, 1), :, 1, size(input, 3))), dims=2)
     kfn.zit .= reshape(_zit, (size(input, 1), :, size(input, 3)))
 
-    # project 3D kfn zit into 4D lif zit
-    i1, i2, i3, i4 = size(kfn.lif_zit)
-    kfn.lif_zit .= reshape(kfn.zit, (i1, i2, 1, i4)) .* kfn.lif_arrayProjection4d
-    
-    lifForward( kfn.lif_zit,
-                kfn.lif_wRec,
-                kfn.lif_vt,
-                kfn.lif_vth,
-                kfn.lif_vRest,
-                kfn.lif_zt4d,
-                kfn.lif_alpha,
-                kfn.lif_phi,
-                kfn.lif_epsilonRec,
-                kfn.lif_refractoryCounter,
-                kfn.lif_refractoryDuration,
-                kfn.lif_gammaPd,
-                kfn.lif_firingCounter,
-                kfn.lif_recSignal,)
-
-    # project 3D kfn zit into 4D alif zit
-    i1, i2, i3, i4 = size(kfn.alif_zit)
-    kfn.alif_zit .= reshape(kfn.zit, (i1, i2, 1, i4)) .* kfn.alif_arrayProjection4d
-    
-    alifForward(kfn.alif_zit,
-                kfn.alif_wRec, 
-                kfn.alif_vt,
-                kfn.alif_vth,
-                kfn.alif_vRest,
-                kfn.alif_zt4d,
-                kfn.alif_alpha,
-                kfn.alif_phi,
-                kfn.alif_epsilonRec,
-                kfn.alif_refractoryCounter,
-                kfn.alif_refractoryDuration,
-                kfn.alif_gammaPd,
-                kfn.alif_firingCounter,
-                kfn.alif_recSignal,
-                kfn.alif_epsilonRecA,
-                kfn.alif_a,
-                kfn.alif_avth,
-                kfn.alif_beta,
-                kfn.alif_rho,)
+    @sync begin
+        @async begin
+                # project 3D kfn zit into 4D lif zit
+                i1, i2, i3, i4 = size(kfn.lif_zit)
+                kfn.lif_zit .= reshape(kfn.zit, (i1, i2, 1, i4)) .* kfn.lif_arrayProjection4d
+                
+                lifForward( kfn.lif_zit,
+                                kfn.lif_wRec,
+                                kfn.lif_vt,
+                                kfn.lif_vth,
+                                kfn.lif_vRest,
+                                kfn.lif_zt4d,
+                                kfn.lif_alpha,
+                                kfn.lif_phi,
+                                kfn.lif_epsilonRec,
+                                kfn.lif_refractoryCounter,
+                                kfn.lif_refractoryDuration,
+                                kfn.lif_gammaPd,
+                                kfn.lif_firingCounter,
+                                kfn.lif_recSignal,)
+        end
+        @async begin
+                # project 3D kfn zit into 4D alif zit
+                i1, i2, i3, i4 = size(kfn.alif_zit)
+                kfn.alif_zit .= reshape(kfn.zit, (i1, i2, 1, i4)) .* kfn.alif_arrayProjection4d
+                
+                alifForward(kfn.alif_zit,
+                                kfn.alif_wRec, 
+                                kfn.alif_vt,
+                                kfn.alif_vth,
+                                kfn.alif_vRest,
+                                kfn.alif_zt4d,
+                                kfn.alif_alpha,
+                                kfn.alif_phi,
+                                kfn.alif_epsilonRec,
+                                kfn.alif_refractoryCounter,
+                                kfn.alif_refractoryDuration,
+                                kfn.alif_gammaPd,
+                                kfn.alif_firingCounter,
+                                kfn.alif_recSignal,
+                                kfn.alif_epsilonRecA,
+                                kfn.alif_a,
+                                kfn.alif_avth,
+                                kfn.alif_beta,
+                                kfn.alif_rho,)
+        end
+    end
     
     # reduce lif_zt4d and alif_zt4d into lif_zt, alif_zt (4d -> 1d)
     kfn.lif_zt .= reduce(max, kfn.lif_zt4d, dims=(1,2))